From 09e4b34dd8640ae36cd28db815c6e80d079ebb32 Mon Sep 17 00:00:00 2001 From: Vas Crabb Date: Tue, 3 Jan 2023 16:05:24 +1100 Subject: [PATCH] Updated png.py to 0.0.20 (last version before Python 3.4 support dropped) --- scripts/build/png.py | 3271 ++++++++++++++++++------------------------ 1 file changed, 1422 insertions(+), 1849 deletions(-) diff --git a/scripts/build/png.py b/scripts/build/png.py index 76798443669..43c6e3c93e0 100644 --- a/scripts/build/png.py +++ b/scripts/build/png.py @@ -31,79 +31,113 @@ # SOFTWARE. """ -Pure Python PNG Reader/Writer +The ``png`` module can read and write PNG files. -This Python module implements support for PNG images (see PNG -specification at http://www.w3.org/TR/2003/REC-PNG-20031110/ ). It reads -and writes PNG files with all allowable bit depths -(1/2/4/8/16/24/32/48/64 bits per pixel) and colour combinations: -greyscale (1/2/4/8/16 bit); RGB, RGBA, LA (greyscale with alpha) with -8/16 bits per channel; colour mapped images (1/2/4/8 bit). -Adam7 interlacing is supported for reading and -writing. A number of optional chunks can be specified (when writing) -and understood (when reading): ``tRNS``, ``bKGD``, ``gAMA``. +Installation and Overview +------------------------- + +``pip install pypng`` For help, type ``import png; help(png)`` in your python interpreter. -A good place to start is the :class:`Reader` and :class:`Writer` -classes. +A good place to start is the :class:`Reader` and :class:`Writer` classes. -Requires Python 2.3. Limited support is available for Python 2.2, but -not everything works. Best with Python 2.4 and higher. Installation is -trivial, but see the ``README.txt`` file (with the source distribution) -for details. +Coverage of PNG formats is fairly complete; +all allowable bit depths (1/2/4/8/16/24/32/48/64 bits per pixel) and +colour combinations are supported: -This file can also be used as a command-line utility to convert -`Netpbm `_ PNM files to PNG, and the -reverse conversion from PNG to PNM. The interface is similar to that -of the ``pnmtopng`` program from Netpbm. Type ``python png.py --help`` -at the shell prompt for usage and a list of options. +- greyscale (1/2/4/8/16 bit); +- RGB, RGBA, LA (greyscale with alpha) with 8/16 bits per channel; +- colour mapped images (1/2/4/8 bit). -A note on spelling and terminology ----------------------------------- +Interlaced images, +which support a progressive display when downloading, +are supported for both reading and writing. -Generally British English spelling is used in the documentation. So -that's "greyscale" and "colour". This not only matches the author's -native language, it's also used by the PNG specification. +A number of optional chunks can be specified (when writing) +and understood (when reading): ``tRNS``, ``bKGD``, ``gAMA``. + +The ``sBIT`` chunk can be used to specify precision for +non-native bit depths. + +Requires Python 3.4 or higher (or Python 2.7). +Installation is trivial, +but see the ``README.txt`` file (with the source distribution) for details. + +Full use of all features will need some reading of the PNG specification +http://www.w3.org/TR/2003/REC-PNG-20031110/. + +The package also comes with command line utilities. + +- ``pripamtopng`` converts + `Netpbm `_ PAM/PNM files to PNG; +- ``pripngtopam`` converts PNG to file PAM/PNM. + +There are a few more for simple PNG manipulations. + +Spelling and Terminology +------------------------ + +Generally British English spelling is used in the documentation. +So that's "greyscale" and "colour". +This not only matches the author's native language, +it's also used by the PNG specification. + +Colour Models +------------- The major colour models supported by PNG (and hence by PyPNG) are: -greyscale, RGB, greyscale--alpha, RGB--alpha. These are sometimes -referred to using the abbreviations: L, RGB, LA, RGBA. In this case -each letter abbreviates a single channel: *L* is for Luminance or Luma -or Lightness which is the channel used in greyscale images; *R*, *G*, -*B* stand for Red, Green, Blue, the components of a colour image; *A* -stands for Alpha, the opacity channel (used for transparency effects, -but higher values are more opaque, so it makes sense to call it -opacity). -A note on formats ------------------ +- greyscale; +- greyscale--alpha; +- RGB; +- RGB--alpha. -When getting pixel data out of this module (reading) and presenting -data to this module (writing) there are a number of ways the data could -be represented as a Python value. Generally this module uses one of -three formats called "flat row flat pixel", "boxed row flat pixel", and -"boxed row boxed pixel". Basically the concern is whether each pixel -and each row comes in its own little tuple (box), or not. +Also referred to using the abbreviations: L, LA, RGB, RGBA. +Each letter codes a single channel: +*L* is for Luminance or Luma or Lightness (greyscale images); +*A* stands for Alpha, the opacity channel +(used for transparency effects, but higher values are more opaque, +so it makes sense to call it opacity); +*R*, *G*, *B* stand for Red, Green, Blue (colour image). + +Lists, arrays, sequences, and so on +----------------------------------- + +When getting pixel data out of this module (reading) and +presenting data to this module (writing) there are +a number of ways the data could be represented as a Python value. + +The preferred format is a sequence of *rows*, +which each row being a sequence of *values*. +In this format, the values are in pixel order, +with all the values from all the pixels in a row +being concatenated into a single sequence for that row. Consider an image that is 3 pixels wide by 2 pixels high, and each pixel has RGB components: -Boxed row flat pixel:: +Sequence of rows:: list([R,G,B, R,G,B, R,G,B], [R,G,B, R,G,B, R,G,B]) -Each row appears as its own list, but the pixels are flattened so -that three values for one pixel simply follow the three values for -the previous pixel. This is the most common format used, because it -provides a good compromise between space and convenience. PyPNG regards -itself as at liberty to replace any sequence type with any sufficiently -compatible other sequence type; in practice each row is an array (from -the array module), and the outer list is sometimes an iterator rather -than an explicit list (so that streaming is possible). +Each row appears as its own list, +but the pixels are flattened so that three values for one pixel +simply follow the three values for the previous pixel. -Flat row flat pixel:: +This is the preferred because +it provides a good compromise between space and convenience. +PyPNG regards itself as at liberty to replace any sequence type with +any sufficiently compatible other sequence type; +in practice each row is an array (``bytearray`` or ``array.array``). + +To allow streaming the outer list is sometimes +an iterator rather than an explicit list. + +An alternative format is a single array holding all the values. + +Array of values:: [R,G,B, R,G,B, R,G,B, R,G,B, R,G,B, R,G,B] @@ -111,64 +145,48 @@ Flat row flat pixel:: The entire image is one single giant sequence of colour values. Generally an array will be used (to save space), not a list. -Boxed row boxed pixel:: +The top row comes first, +and within each row the pixels are ordered from left-to-right. +Within a pixel the values appear in the order R-G-B-A +(or L-A for greyscale--alpha). - list([ (R,G,B), (R,G,B), (R,G,B) ], - [ (R,G,B), (R,G,B), (R,G,B) ]) - -Each row appears in its own list, but each pixel also appears in its own -tuple. A serious memory burn in Python. - -In all cases the top row comes first, and for each row the pixels are -ordered from left-to-right. Within a pixel the values appear in the -order, R-G-B-A (or L-A for greyscale--alpha). - -There is a fourth format, mentioned because it is used internally, -is close to what lies inside a PNG file itself, and has some support -from the public API. This format is called packed. When packed, -each row is a sequence of bytes (integers from 0 to 255), just as -it is before PNG scanline filtering is applied. When the bit depth -is 8 this is essentially the same as boxed row flat pixel; when the -bit depth is less than 8, several pixels are packed into each byte; -when the bit depth is 16 (the only value more than 8 that is supported -by the PNG image format) each pixel value is decomposed into 2 bytes -(and `packed` is a misnomer). This format is used by the -:meth:`Writer.write_packed` method. It isn't usually a convenient -format, but may be just right if the source data for the PNG image -comes from something that uses a similar format (for example, 1-bit -BMPs, or another PNG file). - -And now, my famous members --------------------------- +There is another format, which should only be used with caution. +It is mentioned because it is used internally, +is close to what lies inside a PNG file itself, +and has some support from the public API. +This format is called *packed*. +When packed, each row is a sequence of bytes (integers from 0 to 255), +just as it is before PNG scanline filtering is applied. +When the bit depth is 8 this is the same as a sequence of rows; +when the bit depth is less than 8 (1, 2 and 4), +several pixels are packed into each byte; +when the bit depth is 16 each pixel value is decomposed into 2 bytes +(and `packed` is a misnomer). +This format is used by the :meth:`Writer.write_packed` method. +It isn't usually a convenient format, +but may be just right if the source data for +the PNG image comes from something that uses a similar format +(for example, 1-bit BMPs, or another PNG file). """ -# http://www.python.org/doc/2.2.3/whatsnew/node5.html -from __future__ import generators,print_function +from __future__ import print_function -__version__ = "0.0.17" +__version__ = "0.0.20" -from array import array -try: - from itertools import imap -except ImportError: - imap = map +import collections +import io # For io.BytesIO +import itertools import math # http://www.python.org/doc/2.4.4/lib/module-operator.html import operator +import re import struct import sys -import zlib # http://www.python.org/doc/2.4.4/lib/module-warnings.html import warnings -try: - # `cpngfilters` is a Cython module: it must be compiled by - # Cython for this import to work. - # If this import does work, then it overrides pure-python - # filtering functions defined later in this file (see `class - # pngfilters`). - import cpngfilters as pngfilters -except ImportError: - pass +import zlib + +from array import array __all__ = ['Image', 'Reader', 'Writer', 'write_chunks', 'from_array'] @@ -176,99 +194,53 @@ __all__ = ['Image', 'Reader', 'Writer', 'write_chunks', 'from_array'] # The PNG signature. # http://www.w3.org/TR/PNG/#5PNG-file-signature -_signature = struct.pack('8B', 137, 80, 78, 71, 13, 10, 26, 10) +signature = struct.pack('8B', 137, 80, 78, 71, 13, 10, 26, 10) + +# The xstart, ystart, xstep, ystep for the Adam7 interlace passes. +adam7 = ((0, 0, 8, 8), + (4, 0, 8, 8), + (0, 4, 4, 8), + (2, 0, 4, 4), + (0, 2, 2, 4), + (1, 0, 2, 2), + (0, 1, 1, 2)) + + +def adam7_generate(width, height): + """ + Generate the coordinates for the reduced scanlines + of an Adam7 interlaced image + of size `width` by `height` pixels. + + Yields a generator for each pass, + and each pass generator yields a series of (x, y, xstep) triples, + each one identifying a reduced scanline consisting of + pixels starting at (x, y) and taking every xstep pixel to the right. + """ + + for xstart, ystart, xstep, ystep in adam7: + if xstart >= width: + continue + yield ((xstart, y, xstep) for y in range(ystart, height, ystep)) + + +# Models the 'pHYs' chunk (used by the Reader) +Resolution = collections.namedtuple('_Resolution', 'x y unit_is_meter') -_adam7 = ((0, 0, 8, 8), - (4, 0, 8, 8), - (0, 4, 4, 8), - (2, 0, 4, 4), - (0, 2, 2, 4), - (1, 0, 2, 2), - (0, 1, 1, 2)) def group(s, n): - # See http://www.python.org/doc/2.6/library/functions.html#zip - return zip(*[iter(s)]*n) + return list(zip(* [iter(s)] * n)) + def isarray(x): - """Same as ``isinstance(x, array)`` except on Python 2.2, where it - always returns ``False``. This helps PyPNG work on Python 2.2. - """ + return isinstance(x, array) - try: - return isinstance(x, array) - except TypeError: - # Because on Python 2.2 array.array is not a type. - return False - -try: - array.tobytes -except AttributeError: - try: # see :pyver:old - array.tostring - except AttributeError: - def tostring(row): - l = len(row) - return struct.pack('%dB' % l, *row) - else: - def tostring(row): - """Convert row of bytes to string. Expects `row` to be an - ``array``. - """ - return row.tostring() -else: - def tostring(row): - """ Python3 definition, array.tostring() is deprecated in Python3 - """ - return row.tobytes() - -# Conditionally convert to bytes. Works on Python 2 and Python 3. -try: - bytes('', 'ascii') - def strtobytes(x): return bytes(x, 'iso8859-1') - def bytestostr(x): return str(x, 'iso8859-1') -except (NameError, TypeError): - # We get NameError when bytes() does not exist (most Python - # 2.x versions), and TypeError when bytes() exists but is on - # Python 2.x (when it is an alias for str() and takes at most - # one argument). - strtobytes = str - bytestostr = str - -def interleave_planes(ipixels, apixels, ipsize, apsize): - """ - Interleave (colour) planes, e.g. RGB + A = RGBA. - - Return an array of pixels consisting of the `ipsize` elements of - data from each pixel in `ipixels` followed by the `apsize` elements - of data from each pixel in `apixels`. Conventionally `ipixels` - and `apixels` are byte arrays so the sizes are bytes, but it - actually works with any arrays of the same type. The returned - array is the same type as the input arrays which should be the - same type as each other. - """ - - itotal = len(ipixels) - atotal = len(apixels) - newtotal = itotal + atotal - newpsize = ipsize + apsize - # Set up the output buffer - # See http://www.python.org/doc/2.4.4/lib/module-array.html#l2h-1356 - out = array(ipixels.typecode) - # It's annoying that there is no cheap way to set the array size :-( - out.extend(ipixels) - out.extend(apixels) - # Interleave in the pixel data - for i in range(ipsize): - out[i:newtotal:newpsize] = ipixels[i:itotal:ipsize] - for i in range(apsize): - out[i+ipsize:newtotal:newpsize] = apixels[i:atotal:apsize] - return out def check_palette(palette): - """Check a palette argument (to the :class:`Writer` class) - for validity. Returns the palette as a list if okay; raises an - exception otherwise. + """ + Check a palette argument (to the :class:`Writer` class) for validity. + Returns the palette as a list if okay; + raises an exception otherwise. """ # None is the default and is allowed. @@ -277,25 +249,30 @@ def check_palette(palette): p = list(palette) if not (0 < len(p) <= 256): - raise ValueError("a palette must have between 1 and 256 entries") + raise ProtocolError( + "a palette must have between 1 and 256 entries," + " see https://www.w3.org/TR/PNG/#11PLTE") seen_triple = False - for i,t in enumerate(p): - if len(t) not in (3,4): - raise ValueError( - "palette entry %d: entries must be 3- or 4-tuples." % i) + for i, t in enumerate(p): + if len(t) not in (3, 4): + raise ProtocolError( + "palette entry %d: entries must be 3- or 4-tuples." % i) if len(t) == 3: seen_triple = True if seen_triple and len(t) == 4: - raise ValueError( - "palette entry %d: all 4-tuples must precede all 3-tuples" % i) + raise ProtocolError( + "palette entry %d: all 4-tuples must precede all 3-tuples" % i) for x in t: if int(x) != x or not(0 <= x <= 255): - raise ValueError( - "palette entry %d: values must be integer: 0 <= x <= 255" % i) + raise ProtocolError( + "palette entry %d: " + "values must be integer: 0 <= x <= 255" % i) return p + def check_sizes(size, width, height): - """Check that these arguments, in supplied, are consistent. + """ + Check that these arguments, if supplied, are consistent. Return a (width, height) pair. """ @@ -303,22 +280,25 @@ def check_sizes(size, width, height): return width, height if len(size) != 2: - raise ValueError( - "size argument should be a pair (width, height)") + raise ProtocolError( + "size argument should be a pair (width, height)") if width is not None and width != size[0]: - raise ValueError( - "size[0] (%r) and width (%r) should match when both are used." + raise ProtocolError( + "size[0] (%r) and width (%r) should match when both are used." % (size[0], width)) if height is not None and height != size[1]: - raise ValueError( - "size[1] (%r) and height (%r) should match when both are used." + raise ProtocolError( + "size[1] (%r) and height (%r) should match when both are used." % (size[1], height)) return size + def check_color(c, greyscale, which): - """Checks that a colour argument for transparent or - background options is the right form. Returns the colour - (which, if it's a bar integer, is "corrected" to a 1-tuple). + """ + Checks that a colour argument for transparent or background options + is the right form. + Returns the colour + (which, if it's a bare integer, is "corrected" to a 1-tuple). """ if c is None: @@ -329,33 +309,48 @@ def check_color(c, greyscale, which): except TypeError: c = (c,) if len(c) != 1: - raise ValueError("%s for greyscale must be 1-tuple" % - which) - if not isinteger(c[0]): - raise ValueError( + raise ProtocolError("%s for greyscale must be 1-tuple" % which) + if not is_natural(c[0]): + raise ProtocolError( "%s colour for greyscale must be integer" % which) else: if not (len(c) == 3 and - isinteger(c[0]) and - isinteger(c[1]) and - isinteger(c[2])): - raise ValueError( + is_natural(c[0]) and + is_natural(c[1]) and + is_natural(c[2])): + raise ProtocolError( "%s colour must be a triple of integers" % which) return c + class Error(Exception): def __str__(self): return self.__class__.__name__ + ': ' + ' '.join(self.args) + class FormatError(Error): - """Problem with input file format. In other words, PNG file does - not conform to the specification in some way and is invalid. """ + Problem with input file format. + In other words, PNG file does not conform to + the specification in some way and is invalid. + """ + + +class ProtocolError(Error): + """ + Problem with the way the programming interface has been used, + or the data presented to it. + """ + class ChunkError(FormatError): pass +class Default: + """The default for the greyscale paramter.""" + + class Writer: """ PNG encoder in pure Python. @@ -363,7 +358,7 @@ class Writer: def __init__(self, width=None, height=None, size=None, - greyscale=False, + greyscale=Default, alpha=False, bitdepth=8, palette=None, @@ -372,14 +367,13 @@ class Writer: gamma=None, compression=None, interlace=False, - bytes_per_sample=None, # deprecated planes=None, colormap=None, maxval=None, chunk_limit=2**20, - x_pixels_per_unit = None, - y_pixels_per_unit = None, - unit_is_meter = False): + x_pixels_per_unit=None, + y_pixels_per_unit=None, + unit_is_meter=False): """ Create a PNG encoder object. @@ -390,11 +384,11 @@ class Writer: size Image size (w,h) in pixels, as single argument. greyscale - Input data is greyscale, not RGB. + Pixels are greyscale, not RGB. alpha Input data has alpha channel (RGBA or LA). bitdepth - Bit depth: from 1 to 16. + Bit depth: from 1 to 16 (for each channel). palette Create a palette for a colour mapped image (colour type 3). transparent @@ -410,91 +404,113 @@ class Writer: Create an interlaced image. chunk_limit Write multiple ``IDAT`` chunks to save memory. - x_pixels_per_unit (pHYs chunk) - Number of pixels a unit along the x axis - y_pixels_per_unit (pHYs chunk) - Number of pixels a unit along the y axis - With x_pixel_unit, give the pixel size ratio - unit_is_meter (pHYs chunk) - Indicates if unit is meter or not + x_pixels_per_unit + Number of pixels a unit along the x axis (write a + `pHYs` chunk). + y_pixels_per_unit + Number of pixels a unit along the y axis (write a + `pHYs` chunk). Along with `x_pixel_unit`, this gives + the pixel size ratio. + unit_is_meter + `True` to indicate that the unit (for the `pHYs` + chunk) is metre. The image size (in pixels) can be specified either by using the `width` and `height` arguments, or with the single `size` - argument. If `size` is used it should be a pair (*width*, - *height*). + argument. + If `size` is used it should be a pair (*width*, *height*). - `greyscale` and `alpha` are booleans that specify whether - an image is greyscale (or colour), and whether it has an - alpha channel (or not). + The `greyscale` argument indicates whether input pixels + are greyscale (when true), or colour (when false). + The default is true unless `palette=` is used. + + The `alpha` argument (a boolean) specifies + whether input pixels have an alpha channel (or not). `bitdepth` specifies the bit depth of the source pixel values. - Each source pixel value must be an integer between 0 and - ``2**bitdepth-1``. For example, 8-bit images have values - between 0 and 255. PNG only stores images with bit depths of - 1,2,4,8, or 16. When `bitdepth` is not one of these values, - the next highest valid bit depth is selected, and an ``sBIT`` - (significant bits) chunk is generated that specifies the - original precision of the source image. In this case the - supplied pixel values will be rescaled to fit the range of - the selected bit depth. + Each channel may have a different bit depth. + Each source pixel must have values that are + an integer between 0 and ``2**bitdepth-1``, where + `bitdepth` is the bit depth for the corresponding channel. + For example, 8-bit images have values between 0 and 255. + PNG only stores images with bit depths of + 1,2,4,8, or 16 (the same for all channels). + When `bitdepth` is not one of these values or where + channels have different bit depths, + the next highest valid bit depth is selected, + and an ``sBIT`` (significant bits) chunk is generated + that specifies the original precision of the source image. + In this case the supplied pixel values will be rescaled to + fit the range of the selected bit depth. - The details of which bit depth / colour model combinations the - PNG file format supports directly, are somewhat arcane - (refer to the PNG specification for full details). Briefly: - "small" bit depths (1,2,4) are only allowed with greyscale and - colour mapped images; colour mapped images cannot have bit depth - 16. + The PNG file format supports many bit depth / colour model + combinations, but not all. + The details are somewhat arcane + (refer to the PNG specification for full details). + Briefly: + Bit depths < 8 (1,2,4) are only allowed with greyscale and + colour mapped images; + colour mapped images cannot have bit depth 16. - For colour mapped images (in other words, when the `palette` - argument is specified) the `bitdepth` argument must match one of - the valid PNG bit depths: 1, 2, 4, or 8. (It is valid to have a - PNG image with a palette and an ``sBIT`` chunk, but the meaning - is slightly different; it would be awkward to press the - `bitdepth` argument into service for this.) + For colour mapped images + (in other words, when the `palette` argument is specified) + the `bitdepth` argument must match one of + the valid PNG bit depths: 1, 2, 4, or 8. + (It is valid to have a PNG image with a palette and + an ``sBIT`` chunk, but the meaning is slightly different; + it would be awkward to use the `bitdepth` argument for this.) - The `palette` option, when specified, causes a colour mapped - image to be created: the PNG colour type is set to 3; greyscale - must not be set; alpha must not be set; transparent must not be - set; the bit depth must be 1,2,4, or 8. When a colour mapped - image is created, the pixel values are palette indexes and + The `palette` option, when specified, + causes a colour mapped image to be created: + the PNG colour type is set to 3; + `greyscale` must not be true; `alpha` must not be true; + `transparent` must not be set. + The bit depth must be 1,2,4, or 8. + When a colour mapped image is created, + the pixel values are palette indexes and the `bitdepth` argument specifies the size of these indexes (not the size of the colour values in the palette). The palette argument value should be a sequence of 3- or - 4-tuples. 3-tuples specify RGB palette entries; 4-tuples - specify RGBA palette entries. If both 4-tuples and 3-tuples - appear in the sequence then all the 4-tuples must come - before all the 3-tuples. A ``PLTE`` chunk is created; if there - are 4-tuples then a ``tRNS`` chunk is created as well. The - ``PLTE`` chunk will contain all the RGB triples in the same - sequence; the ``tRNS`` chunk will contain the alpha channel for - all the 4-tuples, in the same sequence. Palette entries - are always 8-bit. + 4-tuples. + 3-tuples specify RGB palette entries; + 4-tuples specify RGBA palette entries. + All the 4-tuples (if present) must come before all the 3-tuples. + A ``PLTE`` chunk is created; + if there are 4-tuples then a ``tRNS`` chunk is created as well. + The ``PLTE`` chunk will contain all the RGB triples in the same + sequence; + the ``tRNS`` chunk will contain the alpha channel for + all the 4-tuples, in the same sequence. + Palette entries are always 8-bit. - If specified, the `transparent` and `background` parameters must - be a tuple with three integer values for red, green, blue, or - a simple integer (or singleton tuple) for a greyscale image. + If specified, the `transparent` and `background` parameters must be + a tuple with one element for each channel in the image. + Either a 3-tuple of integer (RGB) values for a colour image, or + a 1-tuple of a single integer for a greyscale image. If specified, the `gamma` parameter must be a positive number - (generally, a float). A ``gAMA`` chunk will be created. + (generally, a `float`). + A ``gAMA`` chunk will be created. Note that this will not change the values of the pixels as - they appear in the PNG file, they are assumed to have already + they appear in the PNG file, + they are assumed to have already been converted appropriately for the gamma specified. The `compression` argument specifies the compression level to - be used by the ``zlib`` module. Values from 1 to 9 specify - compression, with 9 being "more compressed" (usually smaller - and slower, but it doesn't always work out that way). 0 means - no compression. -1 and ``None`` both mean that the default - level of compession will be picked by the ``zlib`` module - (which is generally acceptable). + be used by the ``zlib`` module. + Values from 1 to 9 (highest) specify compression. + 0 means no compression. + -1 and ``None`` both mean that the ``zlib`` module uses + the default level of compession (which is generally acceptable). If `interlace` is true then an interlaced image is created - (using PNG's so far only interace method, *Adam7*). This does - not affect how the pixels should be presented to the encoder, + (using PNG's so far only interace method, *Adam7*). + This does not affect how the pixels should be passed in, rather it changes how they are arranged into the PNG file. - On slow connexions interlaced images can be partially decoded - by the browser to give a rough view of the image that is + On slow connexions interlaced images can be + partially decoded by the browser to give + a rough view of the image that is successively refined as more image data appears. .. note :: @@ -503,8 +519,9 @@ class Writer: to be processed in working memory. `chunk_limit` is used to limit the amount of memory used whilst - compressing the image. In order to avoid using large amounts of - memory, multiple ``IDAT`` chunks may be created. + compressing the image. + In order to avoid using large amounts of memory, + multiple ``IDAT`` chunks may be created. """ # At the moment the `planes` argument is ignored; @@ -516,85 +533,75 @@ class Writer: width, height = check_sizes(size, width, height) del size + if not is_natural(width) or not is_natural(height): + raise ProtocolError("width and height must be integers") if width <= 0 or height <= 0: - raise ValueError("width and height must be greater than zero") - if not isinteger(width) or not isinteger(height): - raise ValueError("width and height must be integers") + raise ProtocolError("width and height must be greater than zero") # http://www.w3.org/TR/PNG/#7Integers-and-byte-order - if width > 2**32-1 or height > 2**32-1: - raise ValueError("width and height cannot exceed 2**32-1") + if width > 2 ** 31 - 1 or height > 2 ** 31 - 1: + raise ProtocolError("width and height cannot exceed 2**31-1") if alpha and transparent is not None: - raise ValueError( + raise ProtocolError( "transparent colour not allowed with alpha channel") - if bytes_per_sample is not None: - warnings.warn('please use bitdepth instead of bytes_per_sample', - DeprecationWarning) - if bytes_per_sample not in (0.125, 0.25, 0.5, 1, 2): - raise ValueError( - "bytes per sample must be .125, .25, .5, 1, or 2") - bitdepth = int(8*bytes_per_sample) - del bytes_per_sample - if not isinteger(bitdepth) or bitdepth < 1 or 16 < bitdepth: - raise ValueError("bitdepth (%r) must be a positive integer <= 16" % - bitdepth) + # bitdepth is either single integer, or tuple of integers. + # Convert to tuple. + try: + len(bitdepth) + except TypeError: + bitdepth = (bitdepth, ) + for b in bitdepth: + valid = is_natural(b) and 1 <= b <= 16 + if not valid: + raise ProtocolError( + "each bitdepth %r must be a positive integer <= 16" % + (bitdepth,)) - self.rescale = None + # Calculate channels, and + # expand bitdepth to be one element per channel. palette = check_palette(palette) - if palette: - if bitdepth not in (1,2,4,8): - raise ValueError("with palette, bitdepth must be 1, 2, 4, or 8") - if transparent is not None: - raise ValueError("transparent and palette not compatible") - if alpha: - raise ValueError("alpha and palette not compatible") - if greyscale: - raise ValueError("greyscale and palette not compatible") + alpha = bool(alpha) + colormap = bool(palette) + if greyscale is Default and palette: + greyscale = False + greyscale = bool(greyscale) + if colormap: + color_planes = 1 + planes = 1 else: - # No palette, check for sBIT chunk generation. - if alpha or not greyscale: - if bitdepth not in (8,16): - targetbitdepth = (8,16)[bitdepth > 8] - self.rescale = (bitdepth, targetbitdepth) - bitdepth = targetbitdepth - del targetbitdepth - else: - assert greyscale - assert not alpha - if bitdepth not in (1,2,4,8,16): - if bitdepth > 8: - targetbitdepth = 16 - elif bitdepth == 3: - targetbitdepth = 4 - else: - assert bitdepth in (5,6,7) - targetbitdepth = 8 - self.rescale = (bitdepth, targetbitdepth) - bitdepth = targetbitdepth - del targetbitdepth + color_planes = (3, 1)[greyscale] + planes = color_planes + alpha + if len(bitdepth) == 1: + bitdepth *= planes - if bitdepth < 8 and (alpha or not greyscale and not palette): - raise ValueError( - "bitdepth < 8 only permitted with greyscale or palette") - if bitdepth > 8 and palette: - raise ValueError( - "bit depth must be 8 or less for images with palette") + bitdepth, self.rescale = check_bitdepth_rescale( + palette, + bitdepth, + transparent, alpha, greyscale) + + # These are assertions, because above logic should have + # corrected or raised all problematic cases. + if bitdepth < 8: + assert greyscale or palette + assert not alpha + if bitdepth > 8: + assert not palette transparent = check_color(transparent, greyscale, 'transparent') background = check_color(background, greyscale, 'background') - # It's important that the true boolean values (greyscale, alpha, - # colormap, interlace) are converted to bool because Iverson's - # convention is relied upon later on. + # It's important that the true boolean values + # (greyscale, alpha, colormap, interlace) are converted + # to bool because Iverson's convention is relied upon later on. self.width = width self.height = height self.transparent = transparent self.background = background self.gamma = gamma - self.greyscale = bool(greyscale) - self.alpha = bool(alpha) - self.colormap = bool(palette) + self.greyscale = greyscale + self.alpha = alpha + self.colormap = colormap self.bitdepth = int(bitdepth) self.compression = compression self.chunk_limit = chunk_limit @@ -604,135 +611,117 @@ class Writer: self.y_pixels_per_unit = y_pixels_per_unit self.unit_is_meter = bool(unit_is_meter) - self.color_type = 4*self.alpha + 2*(not greyscale) + 1*self.colormap - assert self.color_type in (0,2,3,4,6) + self.color_type = (4 * self.alpha + + 2 * (not greyscale) + + 1 * self.colormap) + assert self.color_type in (0, 2, 3, 4, 6) - self.color_planes = (3,1)[self.greyscale or self.colormap] - self.planes = self.color_planes + self.alpha + self.color_planes = color_planes + self.planes = planes # :todo: fix for bitdepth < 8 - self.psize = (self.bitdepth/8) * self.planes - - def make_palette(self): - """Create the byte sequences for a ``PLTE`` and if necessary a - ``tRNS`` chunk. Returned as a pair (*p*, *t*). *t* will be - ``None`` if no ``tRNS`` chunk is necessary. - """ - - p = array('B') - t = array('B') - - for x in self.palette: - p.extend(x[0:3]) - if len(x) > 3: - t.append(x[3]) - p = tostring(p) - t = tostring(t) - if t: - return p,t - return p,None + self.psize = (self.bitdepth / 8) * self.planes def write(self, outfile, rows): - """Write a PNG image to the output file. `rows` should be - an iterable that yields each row in boxed row flat pixel - format. The rows should be the rows of the original image, - so there should be ``self.height`` rows of ``self.width * - self.planes`` values. If `interlace` is specified (when - creating the instance), then an interlaced PNG file will - be written. Supply the rows in the normal image order; + """ + Write a PNG image to the output file. + `rows` should be an iterable that yields each row + (each row is a sequence of values). + The rows should be the rows of the original image, + so there should be ``self.height`` rows of + ``self.width * self.planes`` values. + If `interlace` is specified (when creating the instance), + then an interlaced PNG file will be written. + Supply the rows in the normal image order; the interlacing is carried out internally. .. note :: - Interlacing will require the entire image to be in working - memory. + Interlacing requires the entire image to be in working memory. """ + # Values per row + vpr = self.width * self.planes + + def check_rows(rows): + """ + Yield each row in rows, + but check each row first (for correct width). + """ + for i, row in enumerate(rows): + try: + wrong_length = len(row) != vpr + except TypeError: + # When using an itertools.ichain object or + # other generator not supporting __len__, + # we set this to False to skip the check. + wrong_length = False + if wrong_length: + # Note: row numbers start at 0. + raise ProtocolError( + "Expected %d values but got %d value, in row %d" % + (vpr, len(row), i)) + yield row + if self.interlace: fmt = 'BH'[self.bitdepth > 8] - a = array(fmt, itertools.chain(*rows)) + a = array(fmt, itertools.chain(*check_rows(rows))) return self.write_array(outfile, a) - nrows = self.write_passes(outfile, rows) + nrows = self.write_passes(outfile, check_rows(rows)) if nrows != self.height: - raise ValueError( - "rows supplied (%d) does not match height (%d)" % - (nrows, self.height)) + raise ProtocolError( + "rows supplied (%d) does not match height (%d)" % + (nrows, self.height)) - def write_passes(self, outfile, rows, packed=False): + def write_passes(self, outfile, rows): """ Write a PNG image to the output file. Most users are expected to find the :meth:`write` or :meth:`write_array` method more convenient. - + The rows should be given to this method in the order that - they appear in the output file. For straightlaced images, - this is the usual top to bottom ordering, but for interlaced - images the rows should have already been interlaced before + they appear in the output file. + For straightlaced images, this is the usual top to bottom ordering. + For interlaced images the rows should have been interlaced before passing them to this function. - `rows` should be an iterable that yields each row. When - `packed` is ``False`` the rows should be in boxed row flat pixel - format; when `packed` is ``True`` each row should be a packed - sequence of bytes. + `rows` should be an iterable that yields each row + (each row being a sequence of values). """ - # http://www.w3.org/TR/PNG/#5PNG-file-signature - outfile.write(_signature) + # Ensure rows are scaled (to 4-/8-/16-bit), + # and packed into bytes. - # http://www.w3.org/TR/PNG/#11IHDR - write_chunk(outfile, 'IHDR', - struct.pack("!2I5B", self.width, self.height, - self.bitdepth, self.color_type, - 0, 0, self.interlace)) - - # See :chunk:order - # http://www.w3.org/TR/PNG/#11gAMA - if self.gamma is not None: - write_chunk(outfile, 'gAMA', - struct.pack("!L", int(round(self.gamma*1e5)))) - - # See :chunk:order - # http://www.w3.org/TR/PNG/#11sBIT if self.rescale: - write_chunk(outfile, 'sBIT', - struct.pack('%dB' % self.planes, - *[self.rescale[0]]*self.planes)) - - # :chunk:order: Without a palette (PLTE chunk), ordering is - # relatively relaxed. With one, gAMA chunk must precede PLTE - # chunk which must precede tRNS and bKGD. - # See http://www.w3.org/TR/PNG/#5ChunkOrdering - if self.palette: - p,t = self.make_palette() - write_chunk(outfile, 'PLTE', p) - if t: - # tRNS chunk is optional. Only needed if palette entries - # have alpha. - write_chunk(outfile, 'tRNS', t) + rows = rescale_rows(rows, self.rescale) - # http://www.w3.org/TR/PNG/#11tRNS - if self.transparent is not None: - if self.greyscale: - write_chunk(outfile, 'tRNS', - struct.pack("!1H", *self.transparent)) - else: - write_chunk(outfile, 'tRNS', - struct.pack("!3H", *self.transparent)) + if self.bitdepth < 8: + rows = pack_rows(rows, self.bitdepth) + elif self.bitdepth == 16: + rows = unpack_rows(rows) - # http://www.w3.org/TR/PNG/#11bKGD - if self.background is not None: - if self.greyscale: - write_chunk(outfile, 'bKGD', - struct.pack("!1H", *self.background)) - else: - write_chunk(outfile, 'bKGD', - struct.pack("!3H", *self.background)) + return self.write_packed(outfile, rows) - # http://www.w3.org/TR/PNG/#11pHYs - if self.x_pixels_per_unit is not None and self.y_pixels_per_unit is not None: - tup = (self.x_pixels_per_unit, self.y_pixels_per_unit, int(self.unit_is_meter)) - write_chunk(outfile, 'pHYs', struct.pack("!LLB",*tup)) + def write_packed(self, outfile, rows): + """ + Write PNG file to `outfile`. + `rows` should be an iterator that yields each packed row; + a packed row being a sequence of packed bytes. + + The rows have a filter byte prefixed and + are then compressed into one or more IDAT chunks. + They are not processed any further, + so if bitdepth is other than 1, 2, 4, 8, 16, + the pixel values should have been scaled + before passing them to this method. + + This method does work for interlaced images but it is best avoided. + For interlaced images, the rows should be + presented in the order that they appear in the file. + """ + + self.write_preamble(outfile) # http://www.w3.org/TR/PNG/#11IDAT if self.compression is not None: @@ -740,195 +729,118 @@ class Writer: else: compressor = zlib.compressobj() - # Choose an extend function based on the bitdepth. The extend - # function packs/decomposes the pixel values into bytes and - # stuffs them onto the data array. - data = array('B') - if self.bitdepth == 8 or packed: - extend = data.extend - elif self.bitdepth == 16: - # Decompose into bytes - def extend(sl): - fmt = '!%dH' % len(sl) - data.extend(array('B', struct.pack(fmt, *sl))) - else: - # Pack into bytes - assert self.bitdepth < 8 - # samples per byte - spb = int(8/self.bitdepth) - def extend(sl): - a = array('B', sl) - # Adding padding bytes so we can group into a whole - # number of spb-tuples. - l = float(len(a)) - extra = math.ceil(l / float(spb))*spb - l - a.extend([0]*int(extra)) - # Pack into bytes - l = group(a, spb) - l = map(lambda e: reduce(lambda x,y: - (x << self.bitdepth) + y, e), l) - data.extend(l) - if self.rescale: - oldextend = extend - factor = \ - float(2**self.rescale[1]-1) / float(2**self.rescale[0]-1) - def extend(sl): - oldextend(map(lambda x: int(round(factor*x)), sl)) + # data accumulates bytes to be compressed for the IDAT chunk; + # it's compressed when sufficiently large. + data = bytearray() - # Build the first row, testing mostly to see if we need to - # changed the extend function to cope with NumPy integer types - # (they cause our ordinary definition of extend to fail, so we - # wrap it). See - # http://code.google.com/p/pypng/issues/detail?id=44 - enumrows = enumerate(rows) - del rows - - # First row's filter type. - data.append(0) - # :todo: Certain exceptions in the call to ``.next()`` or the - # following try would indicate no row data supplied. - # Should catch. - i,row = enumrows.next() - try: - # If this fails... - extend(row) - except: - # ... try a version that converts the values to int first. - # Not only does this work for the (slightly broken) NumPy - # types, there are probably lots of other, unknown, "nearly" - # int types it works for. - def wrapmapint(f): - return lambda sl: f(map(int, sl)) - extend = wrapmapint(extend) - del wrapmapint - extend(row) - - for i,row in enumrows: - # Add "None" filter type. Currently, it's essential that - # this filter type be used for every scanline as we do not - # mark the first row of a reduced pass image; that means we - # could accidentally compute the wrong filtered scanline if - # we used "up", "average", or "paeth" on such a line. + for i, row in enumerate(rows): + # Add "None" filter type. + # Currently, it's essential that this filter type be used + # for every scanline as + # we do not mark the first row of a reduced pass image; + # that means we could accidentally compute + # the wrong filtered scanline if we used + # "up", "average", or "paeth" on such a line. data.append(0) - extend(row) + data.extend(row) if len(data) > self.chunk_limit: - compressed = compressor.compress(tostring(data)) + # :todo: bytes() only necessary in Python 2 + compressed = compressor.compress(bytes(data)) if len(compressed): - write_chunk(outfile, 'IDAT', compressed) - # Because of our very witty definition of ``extend``, - # above, we must re-use the same ``data`` object. Hence - # we use ``del`` to empty this one, rather than create a - # fresh one (which would be my natural FP instinct). - del data[:] - if len(data): - compressed = compressor.compress(tostring(data)) - else: - compressed = strtobytes('') + write_chunk(outfile, b'IDAT', compressed) + data = bytearray() + + compressed = compressor.compress(bytes(data)) flushed = compressor.flush() if len(compressed) or len(flushed): - write_chunk(outfile, 'IDAT', compressed + flushed) + write_chunk(outfile, b'IDAT', compressed + flushed) # http://www.w3.org/TR/PNG/#11IEND - write_chunk(outfile, 'IEND') - return i+1 + write_chunk(outfile, b'IEND') + return i + 1 + + def write_preamble(self, outfile): + # http://www.w3.org/TR/PNG/#5PNG-file-signature + outfile.write(signature) + + # http://www.w3.org/TR/PNG/#11IHDR + write_chunk(outfile, b'IHDR', + struct.pack("!2I5B", self.width, self.height, + self.bitdepth, self.color_type, + 0, 0, self.interlace)) + + # See :chunk:order + # http://www.w3.org/TR/PNG/#11gAMA + if self.gamma is not None: + write_chunk(outfile, b'gAMA', + struct.pack("!L", int(round(self.gamma * 1e5)))) + + # See :chunk:order + # http://www.w3.org/TR/PNG/#11sBIT + if self.rescale: + write_chunk( + outfile, b'sBIT', + struct.pack('%dB' % self.planes, + * [s[0] for s in self.rescale])) + + # :chunk:order: Without a palette (PLTE chunk), + # ordering is relatively relaxed. + # With one, gAMA chunk must precede PLTE chunk + # which must precede tRNS and bKGD. + # See http://www.w3.org/TR/PNG/#5ChunkOrdering + if self.palette: + p, t = make_palette_chunks(self.palette) + write_chunk(outfile, b'PLTE', p) + if t: + # tRNS chunk is optional; + # Only needed if palette entries have alpha. + write_chunk(outfile, b'tRNS', t) + + # http://www.w3.org/TR/PNG/#11tRNS + if self.transparent is not None: + if self.greyscale: + fmt = "!1H" + else: + fmt = "!3H" + write_chunk(outfile, b'tRNS', + struct.pack(fmt, *self.transparent)) + + # http://www.w3.org/TR/PNG/#11bKGD + if self.background is not None: + if self.greyscale: + fmt = "!1H" + else: + fmt = "!3H" + write_chunk(outfile, b'bKGD', + struct.pack(fmt, *self.background)) + + # http://www.w3.org/TR/PNG/#11pHYs + if (self.x_pixels_per_unit is not None and + self.y_pixels_per_unit is not None): + tup = (self.x_pixels_per_unit, + self.y_pixels_per_unit, + int(self.unit_is_meter)) + write_chunk(outfile, b'pHYs', struct.pack("!LLB", *tup)) def write_array(self, outfile, pixels): """ - Write an array in flat row flat pixel format as a PNG file on - the output file. See also :meth:`write` method. + Write an array that holds all the image values + as a PNG file on the output file. + See also :meth:`write` method. """ if self.interlace: + if type(pixels) != array: + # Coerce to array type + fmt = 'BH'[self.bitdepth > 8] + pixels = array(fmt, pixels) self.write_passes(outfile, self.array_scanlines_interlace(pixels)) else: self.write_passes(outfile, self.array_scanlines(pixels)) - def write_packed(self, outfile, rows): - """ - Write PNG file to `outfile`. The pixel data comes from `rows` - which should be in boxed row packed format. Each row should be - a sequence of packed bytes. - - Technically, this method does work for interlaced images but it - is best avoided. For interlaced images, the rows should be - presented in the order that they appear in the file. - - This method should not be used when the source image bit depth - is not one naturally supported by PNG; the bit depth should be - 1, 2, 4, 8, or 16. - """ - - if self.rescale: - raise Error("write_packed method not suitable for bit depth %d" % - self.rescale[0]) - return self.write_passes(outfile, rows, packed=True) - - def convert_pnm(self, infile, outfile): - """ - Convert a PNM file containing raw pixel data into a PNG file - with the parameters set in the writer object. Works for - (binary) PGM, PPM, and PAM formats. - """ - - if self.interlace: - pixels = array('B') - pixels.fromfile(infile, - (self.bitdepth/8) * self.color_planes * - self.width * self.height) - self.write_passes(outfile, self.array_scanlines_interlace(pixels)) - else: - self.write_passes(outfile, self.file_scanlines(infile)) - - def convert_ppm_and_pgm(self, ppmfile, pgmfile, outfile): - """ - Convert a PPM and PGM file containing raw pixel data into a - PNG outfile with the parameters set in the writer object. - """ - pixels = array('B') - pixels.fromfile(ppmfile, - (self.bitdepth/8) * self.color_planes * - self.width * self.height) - apixels = array('B') - apixels.fromfile(pgmfile, - (self.bitdepth/8) * - self.width * self.height) - pixels = interleave_planes(pixels, apixels, - (self.bitdepth/8) * self.color_planes, - (self.bitdepth/8)) - if self.interlace: - self.write_passes(outfile, self.array_scanlines_interlace(pixels)) - else: - self.write_passes(outfile, self.array_scanlines(pixels)) - - def file_scanlines(self, infile): - """ - Generates boxed rows in flat pixel format, from the input file - `infile`. It assumes that the input file is in a "Netpbm-like" - binary format, and is positioned at the beginning of the first - pixel. The number of pixels to read is taken from the image - dimensions (`width`, `height`, `planes`) and the number of bytes - per value is implied by the image `bitdepth`. - """ - - # Values per row - vpr = self.width * self.planes - row_bytes = vpr - if self.bitdepth > 8: - assert self.bitdepth == 16 - row_bytes *= 2 - fmt = '>%dH' % vpr - def line(): - return array('H', struct.unpack(fmt, infile.read(row_bytes))) - else: - def line(): - scanline = array('B', infile.read(row_bytes)) - return scanline - for y in range(self.height): - yield line() - def array_scanlines(self, pixels): """ - Generates boxed rows (flat pixels) from flat rows (flat pixels) - in an array. + Generates rows (each a sequence of values) from + a single array of values. """ # Values per row @@ -941,10 +853,10 @@ class Writer: def array_scanlines_interlace(self, pixels): """ - Generator for interlaced scanlines from an array. `pixels` is - the full source image in flat row flat pixel format. The - generator yields each scanline of the reduced passes in turn, in - boxed row flat pixel format. + Generator for interlaced scanlines from an array. + `pixels` is the full source image as a single array of values. + The generator yields each scanline of the reduced passes in turn, + each scanline being a sequence of values. """ # http://www.w3.org/TR/PNG/#8InterlaceMethods @@ -952,160 +864,225 @@ class Writer: fmt = 'BH'[self.bitdepth > 8] # Value per row vpr = self.width * self.planes - for xstart, ystart, xstep, ystep in _adam7: - if xstart >= self.width: - continue - # Pixels per row (of reduced image) - ppr = int(math.ceil((self.width-xstart)/float(xstep))) - # number of values in reduced image row. - row_len = ppr*self.planes - for y in range(ystart, self.height, ystep): - if xstep == 1: - offset = y * vpr - yield pixels[offset:offset+vpr] - else: - row = array(fmt) - # There's no easier way to set the length of an array - row.extend(pixels[0:row_len]) - offset = y * vpr + xstart * self.planes - end_offset = (y+1) * vpr - skip = self.planes * xstep - for i in range(self.planes): - row[i::self.planes] = \ - pixels[offset+i:end_offset:skip] - yield row -def write_chunk(outfile, tag, data=strtobytes('')): + # Each iteration generates a scanline starting at (x, y) + # and consisting of every xstep pixels. + for lines in adam7_generate(self.width, self.height): + for x, y, xstep in lines: + # Pixels per row (of reduced image) + ppr = int(math.ceil((self.width - x) / float(xstep))) + # Values per row (of reduced image) + reduced_row_len = ppr * self.planes + if xstep == 1: + # Easy case: line is a simple slice. + offset = y * vpr + yield pixels[offset: offset + vpr] + continue + # We have to step by xstep, + # which we can do one plane at a time + # using the step in Python slices. + row = array(fmt) + # There's no easier way to set the length of an array + row.extend(pixels[0:reduced_row_len]) + offset = y * vpr + x * self.planes + end_offset = (y + 1) * vpr + skip = self.planes * xstep + for i in range(self.planes): + row[i::self.planes] = \ + pixels[offset + i: end_offset: skip] + yield row + + +def write_chunk(outfile, tag, data=b''): """ Write a PNG chunk to the output file, including length and checksum. """ + data = bytes(data) # http://www.w3.org/TR/PNG/#5Chunk-layout outfile.write(struct.pack("!I", len(data))) - tag = strtobytes(tag) outfile.write(tag) outfile.write(data) checksum = zlib.crc32(tag) checksum = zlib.crc32(data, checksum) - checksum &= 2**32-1 + checksum &= 2 ** 32 - 1 outfile.write(struct.pack("!I", checksum)) + def write_chunks(out, chunks): """Create a PNG file by writing out the chunks.""" - out.write(_signature) + out.write(signature) for chunk in chunks: write_chunk(out, *chunk) -def filter_scanline(type, line, fo, prev=None): - """Apply a scanline filter to a scanline. `type` specifies the - filter type (0 to 4); `line` specifies the current (unfiltered) - scanline as a sequence of bytes; `prev` specifies the previous - (unfiltered) scanline as a sequence of bytes. `fo` specifies the - filter offset; normally this is size of a pixel in bytes (the number - of bytes per sample times the number of channels), but when this is - < 1 (for bit depths < 8) then the filter offset is 1. + +def rescale_rows(rows, rescale): + """ + Take each row in rows (an iterator) and yield + a fresh row with the pixels scaled according to + the rescale parameters in the list `rescale`. + Each element of `rescale` is a tuple of + (source_bitdepth, target_bitdepth), + with one element per channel. """ - assert 0 <= type < 5 + # One factor for each channel + fs = [float(2 ** s[1] - 1)/float(2 ** s[0] - 1) + for s in rescale] - # The output array. Which, pathetically, we extend one-byte at a - # time (fortunately this is linear). - out = array('B', [type]) + # Assume all target_bitdepths are the same + target_bitdepths = set(s[1] for s in rescale) + assert len(target_bitdepths) == 1 + (target_bitdepth, ) = target_bitdepths + typecode = 'BH'[target_bitdepth > 8] - def sub(): - ai = -fo - for x in line: - if ai >= 0: - x = (x - line[ai]) & 0xff - out.append(x) - ai += 1 - def up(): - for i,x in enumerate(line): - x = (x - prev[i]) & 0xff - out.append(x) - def average(): - ai = -fo - for i,x in enumerate(line): - if ai >= 0: - x = (x - ((line[ai] + prev[i]) >> 1)) & 0xff - else: - x = (x - (prev[i] >> 1)) & 0xff - out.append(x) - ai += 1 - def paeth(): - # http://www.w3.org/TR/PNG/#9Filter-type-4-Paeth - ai = -fo # also used for ci - for i,x in enumerate(line): - a = 0 - b = prev[i] - c = 0 + # Number of channels + n_chans = len(rescale) - if ai >= 0: - a = line[ai] - c = prev[ai] - p = a + b - c - pa = abs(p - a) - pb = abs(p - b) - pc = abs(p - c) - if pa <= pb and pa <= pc: - Pr = a - elif pb <= pc: - Pr = b - else: - Pr = c + for row in rows: + rescaled_row = array(typecode, iter(row)) + for i in range(n_chans): + channel = array( + typecode, + (int(round(fs[i] * x)) for x in row[i::n_chans])) + rescaled_row[i::n_chans] = channel + yield rescaled_row - x = (x - Pr) & 0xff - out.append(x) - ai += 1 - if not prev: - # We're on the first line. Some of the filters can be reduced - # to simpler cases which makes handling the line "off the top" - # of the image simpler. "up" becomes "none"; "paeth" becomes - # "left" (non-trivial, but true). "average" needs to be handled - # specially. - if type == 2: # "up" - type = 0 - elif type == 3: - prev = [0]*len(line) - elif type == 4: # "paeth" - type = 1 - if type == 0: - out.extend(line) - elif type == 1: - sub() - elif type == 2: - up() - elif type == 3: - average() - else: # type == 4 - paeth() - return out +def pack_rows(rows, bitdepth): + """Yield packed rows that are a byte array. + Each byte is packed with the values from several pixels. + """ + + assert bitdepth < 8 + assert 8 % bitdepth == 0 + + # samples per byte + spb = int(8 / bitdepth) + + def make_byte(block): + """Take a block of (2, 4, or 8) values, + and pack them into a single byte. + """ + + res = 0 + for v in block: + res = (res << bitdepth) + v + return res + + for row in rows: + a = bytearray(row) + # Adding padding bytes so we can group into a whole + # number of spb-tuples. + n = float(len(a)) + extra = math.ceil(n / spb) * spb - n + a.extend([0] * int(extra)) + # Pack into bytes. + # Each block is the samples for one byte. + blocks = group(a, spb) + yield bytearray(make_byte(block) for block in blocks) + + +def unpack_rows(rows): + """Unpack each row from being 16-bits per value, + to being a sequence of bytes. + """ + for row in rows: + fmt = '!%dH' % len(row) + yield bytearray(struct.pack(fmt, *row)) + + +def make_palette_chunks(palette): + """ + Create the byte sequences for a ``PLTE`` and + if necessary a ``tRNS`` chunk. + Returned as a pair (*p*, *t*). + *t* will be ``None`` if no ``tRNS`` chunk is necessary. + """ + + p = bytearray() + t = bytearray() + + for x in palette: + p.extend(x[0:3]) + if len(x) > 3: + t.append(x[3]) + if t: + return p, t + return p, None + + +def check_bitdepth_rescale( + palette, bitdepth, transparent, alpha, greyscale): + """ + Returns (bitdepth, rescale) pair. + """ + + if palette: + if len(bitdepth) != 1: + raise ProtocolError( + "with palette, only a single bitdepth may be used") + (bitdepth, ) = bitdepth + if bitdepth not in (1, 2, 4, 8): + raise ProtocolError( + "with palette, bitdepth must be 1, 2, 4, or 8") + if transparent is not None: + raise ProtocolError("transparent and palette not compatible") + if alpha: + raise ProtocolError("alpha and palette not compatible") + if greyscale: + raise ProtocolError("greyscale and palette not compatible") + return bitdepth, None + + # No palette, check for sBIT chunk generation. + + if greyscale and not alpha: + # Single channel, L. + (bitdepth,) = bitdepth + if bitdepth in (1, 2, 4, 8, 16): + return bitdepth, None + if bitdepth > 8: + targetbitdepth = 16 + elif bitdepth == 3: + targetbitdepth = 4 + else: + assert bitdepth in (5, 6, 7) + targetbitdepth = 8 + return targetbitdepth, [(bitdepth, targetbitdepth)] + + assert alpha or not greyscale + + depth_set = tuple(set(bitdepth)) + if depth_set in [(8,), (16,)]: + # No sBIT required. + (bitdepth, ) = depth_set + return bitdepth, None + + targetbitdepth = (8, 16)[max(bitdepth) > 8] + return targetbitdepth, [(b, targetbitdepth) for b in bitdepth] + + +# Regex for decoding mode string +RegexModeDecode = re.compile("(LA?|RGBA?);?([0-9]*)", flags=re.IGNORECASE) def from_array(a, mode=None, info={}): - """Create a PNG :class:`Image` object from a 2- or 3-dimensional - array. One application of this function is easy PIL-style saving: + """ + Create a PNG :class:`Image` object from a 2-dimensional array. + One application of this function is easy PIL-style saving: ``png.from_array(pixels, 'L').save('foo.png')``. - .. note : - - The use of the term *3-dimensional* is for marketing purposes - only. It doesn't actually work. Please bear with us. Meanwhile - enjoy the complimentary snacks (on request) and please use a - 2-dimensional array. - - Unless they are specified using the *info* parameter, the PNG's - height and width are taken from the array size. For a 3 dimensional - array the first axis is the height; the second axis is the width; - and the third axis is the channel number. Thus an RGB image that is - 16 pixels high and 8 wide will use an array that is 16x8x3. For 2 - dimensional arrays the first axis is the height, but the second axis - is ``width*channels``, so an RGB image that is 16 pixels high and 8 - wide will use a 2-dimensional array that is 16x24 (each row will be - 8*3==24 sample values). + Unless they are specified using the *info* parameter, + the PNG's height and width are taken from the array size. + The first axis is the height; the second axis is the + ravelled width and channel index. + The array is treated is a sequence of rows, + each row being a sequence of values (``width*channels`` in number). + So an RGB image that is 16 pixels high and 8 wide will + occupy a 2-dimensional array that is 16x24 + (each row will be 8*3 = 24 sample values). *mode* is a string that specifies the image colour format in a PIL-style mode. It can be: @@ -1119,54 +1096,59 @@ def from_array(a, mode=None, info={}): ``'RGBA'`` colour image with alpha (4 channel) - The mode string can also specify the bit depth (overriding how this - function normally derives the bit depth, see below). Appending - ``';16'`` to the mode will cause the PNG to be 16 bits per channel; + The mode string can also specify the bit depth + (overriding how this function normally derives the bit depth, + see below). + Appending ``';16'`` to the mode will cause the PNG to be + 16 bits per channel; any decimal from 1 to 16 can be used to specify the bit depth. When a 2-dimensional array is used *mode* determines how many channels the image has, and so allows the width to be derived from the second array dimension. - The array is expected to be a ``numpy`` array, but it can be any - suitable Python sequence. For example, a list of lists can be used: - ``png.from_array([[0, 255, 0], [255, 0, 255]], 'L')``. The exact - rules are: ``len(a)`` gives the first dimension, height; - ``len(a[0])`` gives the second dimension; ``len(a[0][0])`` gives the - third dimension, unless an exception is raised in which case a - 2-dimensional array is assumed. It's slightly more complicated than - that because an iterator of rows can be used, and it all still - works. Using an iterator allows data to be streamed efficiently. + The array is expected to be a ``numpy`` array, + but it can be any suitable Python sequence. + For example, a list of lists can be used: + ``png.from_array([[0, 255, 0], [255, 0, 255]], 'L')``. + The exact rules are: ``len(a)`` gives the first dimension, height; + ``len(a[0])`` gives the second dimension. + It's slightly more complicated than that because + an iterator of rows can be used, and it all still works. + Using an iterator allows data to be streamed efficiently. - The bit depth of the PNG is normally taken from the array element's - datatype (but if *mode* specifies a bitdepth then that is used - instead). The array element's datatype is determined in a way which + The bit depth of the PNG is normally taken from + the array element's datatype + (but if *mode* specifies a bitdepth then that is used instead). + The array element's datatype is determined in a way which is supposed to work both for ``numpy`` arrays and for Python - ``array.array`` objects. A 1 byte datatype will give a bit depth of - 8, a 2 byte datatype will give a bit depth of 16. If the datatype - does not have an implicit size, for example it is a plain Python - list of lists, as above, then a default of 8 is used. + ``array.array`` objects. + A 1 byte datatype will give a bit depth of 8, + a 2 byte datatype will give a bit depth of 16. + If the datatype does not have an implicit size, + like the above example where it is a plain Python list of lists, + then a default of 8 is used. + + The *info* parameter is a dictionary that can + be used to specify metadata (in the same style as + the arguments to the :class:`png.Writer` class). + For this function the keys that are useful are: - The *info* parameter is a dictionary that can be used to specify - metadata (in the same style as the arguments to the - :class:``png.Writer`` class). For this function the keys that are - useful are: - height - overrides the height derived from the array dimensions and allows - *a* to be an iterable. + overrides the height derived from the array dimensions and + allows *a* to be an iterable. width overrides the width derived from the array dimensions. bitdepth - overrides the bit depth derived from the element datatype (but - must match *mode* if that also specifies a bit depth). + overrides the bit depth derived from the element datatype + (but must match *mode* if that also specifies a bit depth). - Generally anything specified in the - *info* dictionary will override any implicit choices that this - function would otherwise make, but must match any explicit ones. + Generally anything specified in the *info* dictionary will + override any implicit choices that this function would otherwise make, + but must match any explicit ones. For example, if the *info* dictionary has a ``greyscale`` key then - this must be true when mode is ``'L'`` or ``'LA'`` and false when - mode is ``'RGB'`` or ``'RGBA'``. + this must be true when mode is ``'L'`` or ``'LA'`` and + false when mode is ``'RGB'`` or ``'RGBA'``. """ # We abuse the *info* parameter by modifying it. Take a copy here. @@ -1174,69 +1156,51 @@ def from_array(a, mode=None, info={}): info = dict(info) # Syntax check mode string. - bitdepth = None - try: - # Assign the 'L' or 'RGBA' part to `gotmode`. - if mode.startswith('L'): - gotmode = 'L' - mode = mode[1:] - elif mode.startswith('RGB'): - gotmode = 'RGB' - mode = mode[3:] - else: - raise Error() - if mode.startswith('A'): - gotmode += 'A' - mode = mode[1:] - - # Skip any optional ';' - while mode.startswith(';'): - mode = mode[1:] - - # Parse optional bitdepth - if mode: - try: - bitdepth = int(mode) - except (TypeError, ValueError): - raise Error() - except Error: + match = RegexModeDecode.match(mode) + if not match: raise Error("mode string should be 'RGB' or 'L;16' or similar.") - mode = gotmode + + mode, bitdepth = match.groups() + if bitdepth: + bitdepth = int(bitdepth) + + # Colour format. + if 'greyscale' in info: + if bool(info['greyscale']) != ('L' in mode): + raise ProtocolError("info['greyscale'] should match mode.") + info['greyscale'] = 'L' in mode + + alpha = 'A' in mode + if 'alpha' in info: + if bool(info['alpha']) != alpha: + raise ProtocolError("info['alpha'] should match mode.") + info['alpha'] = alpha # Get bitdepth from *mode* if possible. if bitdepth: - if info.get('bitdepth') and bitdepth != info['bitdepth']: - raise Error("mode bitdepth (%d) should match info bitdepth (%d)." % - (bitdepth, info['bitdepth'])) + if info.get("bitdepth") and bitdepth != info['bitdepth']: + raise ProtocolError( + "bitdepth (%d) should match bitdepth of info (%d)." % + (bitdepth, info['bitdepth'])) info['bitdepth'] = bitdepth # Fill in and/or check entries in *info*. # Dimensions. - if 'size' in info: - # Check width, height, size all match where used. - for dimension,axis in [('width', 0), ('height', 1)]: - if dimension in info: - if info[dimension] != info['size'][axis]: - raise Error( - "info[%r] should match info['size'][%r]." % - (dimension, axis)) - info['width'],info['height'] = info['size'] - if 'height' not in info: + width, height = check_sizes( + info.get("size"), + info.get("width"), + info.get("height")) + if width: + info["width"] = width + if height: + info["height"] = height + + if "height" not in info: try: - l = len(a) + info['height'] = len(a) except TypeError: - raise Error( - "len(a) does not work, supply info['height'] instead.") - info['height'] = l - # Colour format. - if 'greyscale' in info: - if bool(info['greyscale']) != ('L' in mode): - raise Error("info['greyscale'] should match mode.") - info['greyscale'] = 'L' in mode - if 'alpha' in info: - if bool(info['alpha']) != ('A' in mode): - raise Error("info['alpha'] should match mode.") - info['alpha'] = 'A' in mode + raise ProtocolError( + "len(a) does not work, supply info['height'] instead.") planes = len(mode) if 'planes' in info: @@ -1246,25 +1210,14 @@ def from_array(a, mode=None, info={}): # In order to work out whether we the array is 2D or 3D we need its # first row, which requires that we take a copy of its iterator. # We may also need the first row to derive width and bitdepth. - a,t = itertools.tee(a) - row = t.next() + a, t = itertools.tee(a) + row = next(t) del t - try: - row[0][0] - threed = True - testelement = row[0] - except (IndexError, TypeError): - threed = False - testelement = row - if 'width' not in info: - if threed: - width = len(row) - else: - width = len(row) // planes - info['width'] = width - # Not implemented yet - assert not threed + testelement = row + if 'width' not in info: + width = len(row) // planes + info['width'] = width if 'bitdepth' not in info: try: @@ -1275,25 +1228,28 @@ def from_array(a, mode=None, info={}): # Try a Python array.array. bitdepth = 8 * testelement.itemsize except AttributeError: - # We can't determine it from the array element's - # datatype, use a default of 8. + # We can't determine it from the array element's datatype, + # use a default of 8. bitdepth = 8 else: - # If we got here without exception, we now assume that - # the array is a numpy array. + # If we got here without exception, + # we now assume that the array is a numpy array. if dtype.kind == 'b': bitdepth = 1 else: bitdepth = 8 * dtype.itemsize info['bitdepth'] = bitdepth - for thing in 'width height bitdepth greyscale alpha'.split(): + for thing in ["width", "height", "bitdepth", "greyscale", "alpha"]: assert thing in info + return Image(a, info) + # So that refugee's from PIL feel more at home. Not documented. fromarray = from_array + class Image: """A PNG image. You can create an :class:`Image` object from an array of pixels by calling :meth:`png.from_array`. It can be @@ -1303,78 +1259,70 @@ class Image: def __init__(self, rows, info): """ .. note :: - + The constructor is not public. Please do not call it. """ - + self.rows = rows self.info = info def save(self, file): - """Save the image to *file*. If *file* looks like an open file - descriptor then it is used, otherwise it is treated as a - filename and a fresh file is opened. + """Save the image to the named *file*. - In general, you can only call this method once; after it has - been called the first time and the PNG image has been saved, the - source data will have been streamed, and cannot be streamed - again. + See `.write()` if you already have an open file object. + + In general, you can only call this method once; + after it has been called the first time the PNG image is written, + the source data will have been streamed, and + cannot be streamed again. """ w = Writer(**self.info) - try: - file.write - def close(): pass - except AttributeError: - file = open(file, 'wb') - def close(): file.close() + with open(file, 'wb') as fd: + w.write(fd, self.rows) - try: - w.write(file, self.rows) - finally: - close() + def write(self, file): + """Write the image to the open file object. -class _readable: - """ - A simple file-like interface for strings and arrays. - """ + See `.save()` if you have a filename. - def __init__(self, buf): - self.buf = buf - self.offset = 0 + In general, you can only call this method once; + after it has been called the first time the PNG image is written, + the source data will have been streamed, and + cannot be streamed again. + """ - def read(self, n): - r = self.buf[self.offset:self.offset+n] - if isarray(r): - r = r.tostring() - self.offset += n - return r + w = Writer(**self.info) + w.write(file, self.rows) class Reader: """ - PNG decoder in pure Python. + Pure Python PNG decoder in pure Python. """ - def __init__(self, _guess=None, **kw): + def __init__(self, _guess=None, filename=None, file=None, bytes=None): """ - Create a PNG decoder object. - - The constructor expects exactly one keyword argument. If you - supply a positional argument instead, it will guess the input - type. You can choose among the following keyword arguments: + The constructor expects exactly one keyword argument. + If you supply a positional argument instead, + it will guess the input type. + Choose from the following keyword arguments: filename Name of input file (a PNG file). file A file-like object (object with a read() method). bytes - ``array`` or ``string`` with PNG data. + ``bytes`` or ``bytearray`` with PNG data. """ - if ((_guess is not None and len(kw) != 0) or - (_guess is None and len(kw) != 1)): + keywords_supplied = ( + (_guess is not None) + + (filename is not None) + + (file is not None) + + (bytes is not None)) + if keywords_supplied != 1: raise TypeError("Reader() takes exactly 1 argument") # Will be the first 8 bytes, later on. See validate_signature. @@ -1382,80 +1330,76 @@ class Reader: self.transparent = None # A pair of (len,type) if a chunk has been read but its data and # checksum have not (in other words the file position is just - # past the 4 bytes that specify the chunk type). See preamble - # method for how this is used. + # past the 4 bytes that specify the chunk type). + # See preamble method for how this is used. self.atchunk = None if _guess is not None: if isarray(_guess): - kw["bytes"] = _guess + bytes = _guess elif isinstance(_guess, str): - kw["filename"] = _guess + filename = _guess elif hasattr(_guess, 'read'): - kw["file"] = _guess + file = _guess - if "filename" in kw: - self.file = open(kw["filename"], "rb") - elif "file" in kw: - self.file = kw["file"] - elif "bytes" in kw: - self.file = _readable(kw["bytes"]) + if bytes is not None: + self.file = io.BytesIO(bytes) + elif filename is not None: + self.file = open(filename, "rb") + elif file is not None: + self.file = file else: - raise TypeError("expecting filename, file or bytes array") + raise ProtocolError("expecting filename, file or bytes array") - - def chunk(self, seek=None, lenient=False): + def chunk(self, lenient=False): """ - Read the next PNG chunk from the input file; returns a - (*type*,*data*) tuple. *type* is the chunk's type as a string - (all PNG chunk types are 4 characters long). *data* is the - chunk's data content, as a string. + Read the next PNG chunk from the input file; + returns a (*type*, *data*) tuple. + *type* is the chunk's type as a byte string + (all PNG chunk types are 4 bytes long). + *data* is the chunk's data content, as a byte string. - If the optional `seek` argument is - specified then it will keep reading chunks until it either runs - out of file or finds the type specified by the argument. Note - that in general the order of chunks in PNGs is unspecified, so - using `seek` can cause you to miss chunks. - - If the optional `lenient` argument evaluates to True, + If the optional `lenient` argument evaluates to `True`, checksum failures will raise warnings rather than exceptions. """ self.validate_signature() - while True: - # http://www.w3.org/TR/PNG/#5Chunk-layout - if not self.atchunk: - self.atchunk = self.chunklentype() - length,type = self.atchunk - self.atchunk = None - data = self.file.read(length) - if len(data) != length: - raise ChunkError('Chunk %s too short for required %i octets.' - % (type, length)) - checksum = self.file.read(4) - if len(checksum) != 4: - raise ChunkError('Chunk %s too short for checksum.' % type) - if seek and type != seek: - continue - verify = zlib.crc32(strtobytes(type)) - verify = zlib.crc32(data, verify) - # Whether the output from zlib.crc32 is signed or not varies - # according to hideous implementation details, see - # http://bugs.python.org/issue1202 . - # We coerce it to be positive here (in a way which works on - # Python 2.3 and older). - verify &= 2**32 - 1 - verify = struct.pack('!I', verify) - if checksum != verify: - (a, ) = struct.unpack('!I', checksum) - (b, ) = struct.unpack('!I', verify) - message = "Checksum error in %s chunk: 0x%08X != 0x%08X." % (type, a, b) - if lenient: - warnings.warn(message, RuntimeWarning) - else: - raise ChunkError(message) - return type, data + # http://www.w3.org/TR/PNG/#5Chunk-layout + if not self.atchunk: + self.atchunk = self._chunk_len_type() + if not self.atchunk: + raise ChunkError("No more chunks.") + length, type = self.atchunk + self.atchunk = None + + data = self.file.read(length) + if len(data) != length: + raise ChunkError( + 'Chunk %s too short for required %i octets.' + % (type, length)) + checksum = self.file.read(4) + if len(checksum) != 4: + raise ChunkError('Chunk %s too short for checksum.' % type) + verify = zlib.crc32(type) + verify = zlib.crc32(data, verify) + # Whether the output from zlib.crc32 is signed or not varies + # according to hideous implementation details, see + # http://bugs.python.org/issue1202 . + # We coerce it to be positive here (in a way which works on + # Python 2.3 and older). + verify &= 2**32 - 1 + verify = struct.pack('!I', verify) + if checksum != verify: + (a, ) = struct.unpack('!I', checksum) + (b, ) = struct.unpack('!I', verify) + message = ("Checksum error in %s chunk: 0x%08X != 0x%08X." + % (type.decode('ascii'), a, b)) + if lenient: + warnings.warn(message, RuntimeWarning) + else: + raise ChunkError(message) + return type, data def chunks(self): """Return an iterator that will yield each chunk as a @@ -1463,38 +1407,40 @@ class Reader: """ while True: - t,v = self.chunk() - yield t,v - if t == 'IEND': + t, v = self.chunk() + yield t, v + if t == b'IEND': break def undo_filter(self, filter_type, scanline, previous): - """Undo the filter for a scanline. `scanline` is a sequence of - bytes that does not include the initial filter type byte. - `previous` is decoded previous scanline (for straightlaced - images this is the previous pixel row, but for interlaced - images, it is the previous scanline in the reduced image, which - in general is not the previous pixel row in the final image). - When there is no previous scanline (the first row of a - straightlaced image, or the first row in one of the passes in an - interlaced image), then this argument should be ``None``. + """ + Undo the filter for a scanline. + `scanline` is a sequence of bytes that + does not include the initial filter type byte. + `previous` is decoded previous scanline + (for straightlaced images this is the previous pixel row, + but for interlaced images, it is + the previous scanline in the reduced image, + which in general is not the previous pixel row in the final image). + When there is no previous scanline + (the first row of a straightlaced image, + or the first row in one of the passes in an interlaced image), + then this argument should be ``None``. - The scanline will have the effects of filtering removed, and the - result will be returned as a fresh sequence of bytes. + The scanline will have the effects of filtering removed; + the result will be returned as a fresh sequence of bytes. """ # :todo: Would it be better to update scanline in place? - # Yes, with the Cython extension making the undo_filter fast, - # updating scanline inplace makes the code 3 times faster - # (reading 50 images of 800x800 went from 40s to 16s) result = scanline if filter_type == 0: return result - if filter_type not in (1,2,3,4): - raise FormatError('Invalid PNG Filter Type.' - ' See http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters .') + if filter_type not in (1, 2, 3, 4): + raise FormatError( + 'Invalid PNG Filter Type. ' + 'See http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters .') # Filter unit. The stride from one pixel to the corresponding # byte from the previous pixel. Normally this is the pixel @@ -1507,250 +1453,176 @@ class Reader: # first line 'up' is the same as 'null', 'paeth' is the same # as 'sub', with only 'average' requiring any special case. if not previous: - previous = array('B', [0]*len(scanline)) - - def sub(): - """Undo sub filter.""" - - ai = 0 - # Loop starts at index fu. Observe that the initial part - # of the result is already filled in correctly with - # scanline. - for i in range(fu, len(result)): - x = scanline[i] - a = result[ai] - result[i] = (x + a) & 0xff - ai += 1 - - def up(): - """Undo up filter.""" - - for i in range(len(result)): - x = scanline[i] - b = previous[i] - result[i] = (x + b) & 0xff - - def average(): - """Undo average filter.""" - - ai = -fu - for i in range(len(result)): - x = scanline[i] - if ai < 0: - a = 0 - else: - a = result[ai] - b = previous[i] - result[i] = (x + ((a + b) >> 1)) & 0xff - ai += 1 - - def paeth(): - """Undo Paeth filter.""" - - # Also used for ci. - ai = -fu - for i in range(len(result)): - x = scanline[i] - if ai < 0: - a = c = 0 - else: - a = result[ai] - c = previous[ai] - b = previous[i] - p = a + b - c - pa = abs(p - a) - pb = abs(p - b) - pc = abs(p - c) - if pa <= pb and pa <= pc: - pr = a - elif pb <= pc: - pr = b - else: - pr = c - result[i] = (x + pr) & 0xff - ai += 1 + previous = bytearray([0] * len(scanline)) # Call appropriate filter algorithm. Note that 0 has already # been dealt with. - (None, - pngfilters.undo_filter_sub, - pngfilters.undo_filter_up, - pngfilters.undo_filter_average, - pngfilters.undo_filter_paeth)[filter_type](fu, scanline, previous, result) + fn = (None, + undo_filter_sub, + undo_filter_up, + undo_filter_average, + undo_filter_paeth)[filter_type] + fn(fu, scanline, previous, result) return result - def deinterlace(self, raw): + def _deinterlace(self, raw): """ Read raw pixel data, undo filters, deinterlace, and flatten. - Return in flat row flat pixel format. + Return a single array of values. """ # Values per row (of the target image) vpr = self.width * self.planes - # Make a result array, and make it big enough. Interleaving - # writes to the output array randomly (well, not quite), so the - # entire output array must be in memory. - fmt = 'BH'[self.bitdepth > 8] - a = array(fmt, [0]*vpr*self.height) + # Values per image + vpi = vpr * self.height + # Interleaving writes to the output array randomly + # (well, not quite), so the entire output array must be in memory. + # Make a result array, and make it big enough. + if self.bitdepth > 8: + a = array('H', [0] * vpi) + else: + a = bytearray([0] * vpi) source_offset = 0 - for xstart, ystart, xstep, ystep in _adam7: - if xstart >= self.width: - continue - # The previous (reconstructed) scanline. None at the - # beginning of a pass to indicate that there is no previous - # line. + for lines in adam7_generate(self.width, self.height): + # The previous (reconstructed) scanline. + # `None` at the beginning of a pass + # to indicate that there is no previous line. recon = None - # Pixels per row (reduced pass image) - ppr = int(math.ceil((self.width-xstart)/float(xstep))) - # Row size in bytes for this pass. - row_size = int(math.ceil(self.psize * ppr)) - for y in range(ystart, self.height, ystep): + for x, y, xstep in lines: + # Pixels per row (reduced pass image) + ppr = int(math.ceil((self.width - x) / float(xstep))) + # Row size in bytes for this pass. + row_size = int(math.ceil(self.psize * ppr)) + filter_type = raw[source_offset] source_offset += 1 - scanline = raw[source_offset:source_offset+row_size] + scanline = raw[source_offset: source_offset + row_size] source_offset += row_size recon = self.undo_filter(filter_type, scanline, recon) # Convert so that there is one element per pixel value - flat = self.serialtoflat(recon, ppr) + flat = self._bytes_to_values(recon, width=ppr) if xstep == 1: - assert xstart == 0 + assert x == 0 offset = y * vpr - a[offset:offset+vpr] = flat + a[offset: offset + vpr] = flat else: - offset = y * vpr + xstart * self.planes - end_offset = (y+1) * vpr + offset = y * vpr + x * self.planes + end_offset = (y + 1) * vpr skip = self.planes * xstep for i in range(self.planes): - a[offset+i:end_offset:skip] = \ - flat[i::self.planes] + a[offset + i: end_offset: skip] = \ + flat[i:: self.planes] + return a - def iterboxed(self, rows): - """Iterator that yields each scanline in boxed row flat pixel - format. `rows` should be an iterator that yields the bytes of - each row in turn. + def _iter_bytes_to_values(self, byte_rows): + """ + Iterator that yields each scanline; + each scanline being a sequence of values. + `byte_rows` should be an iterator that yields + the bytes of each row in turn. """ - def asvalues(raw): - """Convert a row of raw bytes into a flat row. Result will - be a freshly allocated object, not shared with - argument. - """ + for row in byte_rows: + yield self._bytes_to_values(row) - if self.bitdepth == 8: - return array('B', raw) - if self.bitdepth == 16: - raw = tostring(raw) - return array('H', struct.unpack('!%dH' % (len(raw)//2), raw)) - assert self.bitdepth < 8 - width = self.width - # Samples per byte - spb = 8//self.bitdepth - out = array('B') - mask = 2**self.bitdepth - 1 - shifts = list(map(self.bitdepth.__mul__, reversed(range(spb)))) - for o in raw: - out.extend(list(map(lambda i: mask&(o>>i), shifts))) - return out[:width] - return itertools.imap(asvalues, rows) - - def serialtoflat(self, bytes, width=None): - """Convert serial format (byte stream) pixel data to flat row - flat pixel. + def _bytes_to_values(self, bs, width=None): + """Convert a packed row of bytes into a row of values. + Result will be a freshly allocated object, + not shared with the argument. """ if self.bitdepth == 8: - return bytes + return bytearray(bs) if self.bitdepth == 16: - bytes = tostring(bytes) return array('H', - struct.unpack('!%dH' % (len(bytes)//2), bytes)) + struct.unpack('!%dH' % (len(bs) // 2), bs)) + assert self.bitdepth < 8 if width is None: width = self.width # Samples per byte - spb = 8//self.bitdepth - out = array('B') + spb = 8 // self.bitdepth + out = bytearray() mask = 2**self.bitdepth - 1 - shifts = map(self.bitdepth.__mul__, reversed(range(spb))) - l = width - for o in bytes: - out.extend([(mask&(o>>s)) for s in shifts][:l]) - l -= spb - if l <= 0: - l = width - return out + shifts = [self.bitdepth * i + for i in reversed(list(range(spb)))] + for o in bs: + out.extend([mask & (o >> i) for i in shifts]) + return out[:width] - def iterstraight(self, raw): - """Iterator that undoes the effect of filtering, and yields - each row in serialised format (as a sequence of bytes). - Assumes input is straightlaced. `raw` should be an iterable - that yields the raw bytes in chunks of arbitrary size. + def _iter_straight_packed(self, byte_blocks): + """Iterator that undoes the effect of filtering; + yields each row as a sequence of packed bytes. + Assumes input is straightlaced. + `byte_blocks` should be an iterable that yields the raw bytes + in blocks of arbitrary size. """ # length of row, in bytes rb = self.row_bytes - a = array('B') - # The previous (reconstructed) scanline. None indicates first - # line of image. + a = bytearray() + # The previous (reconstructed) scanline. + # None indicates first line of image. recon = None - for some in raw: - a.extend(some) + for some_bytes in byte_blocks: + a.extend(some_bytes) while len(a) >= rb + 1: filter_type = a[0] - scanline = a[1:rb+1] - del a[:rb+1] + scanline = a[1: rb + 1] + del a[: rb + 1] recon = self.undo_filter(filter_type, scanline, recon) yield recon if len(a) != 0: # :file:format We get here with a file format error: # when the available bytes (after decompressing) do not # pack into exact rows. - raise FormatError( - 'Wrong size for decompressed IDAT chunk.') + raise FormatError('Wrong size for decompressed IDAT chunk.') assert len(a) == 0 def validate_signature(self): - """If signature (header) has not been read then read and + """ + If signature (header) has not been read then read and validate it; otherwise do nothing. """ if self.signature: return self.signature = self.file.read(8) - if self.signature != _signature: + if self.signature != signature: raise FormatError("PNG file has invalid signature.") def preamble(self, lenient=False): """ - Extract the image metadata by reading the initial part of - the PNG file up to the start of the ``IDAT`` chunk. All the - chunks that precede the ``IDAT`` chunk are read and either - processed for metadata or discarded. + Extract the image metadata by reading + the initial part of the PNG file up to + the start of the ``IDAT`` chunk. + All the chunks that precede the ``IDAT`` chunk are + read and either processed for metadata or discarded. - If the optional `lenient` argument evaluates to True, checksum - failures will raise warnings rather than exceptions. + If the optional `lenient` argument evaluates to `True`, + checksum failures will raise warnings rather than exceptions. """ self.validate_signature() while True: if not self.atchunk: - self.atchunk = self.chunklentype() + self.atchunk = self._chunk_len_type() if self.atchunk is None: - raise FormatError( - 'This PNG file has no IDAT chunks.') - if self.atchunk[1] == 'IDAT': + raise FormatError('This PNG file has no IDAT chunks.') + if self.atchunk[1] == b'IDAT': return self.process_chunk(lenient=lenient) - def chunklentype(self): - """Reads just enough of the input to determine the next - chunk's length and type, returned as a (*length*, *type*) pair - where *type* is a string. If there are no more chunks, ``None`` - is returned. + def _chunk_len_type(self): + """ + Reads just enough of the input to + determine the next chunk's length and type; + return a (*length*, *type*) pair where *type* is a byte sequence. + If there are no more chunks, ``None`` is returned. """ x = self.file.read(8) @@ -1758,24 +1630,32 @@ class Reader: return None if len(x) != 8: raise FormatError( - 'End of file whilst reading chunk length and type.') - length,type = struct.unpack('!I4s', x) - type = bytestostr(type) - if length > 2**31-1: - raise FormatError('Chunk %s is too large: %d.' % (type,length)) - return length,type + 'End of file whilst reading chunk length and type.') + length, type = struct.unpack('!I4s', x) + if length > 2 ** 31 - 1: + raise FormatError('Chunk %s is too large: %d.' % (type, length)) + # Check that all bytes are in valid ASCII range. + # https://www.w3.org/TR/2003/REC-PNG-20031110/#5Chunk-layout + type_bytes = set(bytearray(type)) + if not(type_bytes <= set(range(65, 91)) | set(range(97, 123))): + raise FormatError( + 'Chunk %r has invalid Chunk Type.' + % list(type)) + return length, type def process_chunk(self, lenient=False): - """Process the next chunk and its data. This only processes the - following chunk types, all others are ignored: ``IHDR``, - ``PLTE``, ``bKGD``, ``tRNS``, ``gAMA``, ``sBIT``, ``pHYs``. + """ + Process the next chunk and its data. + This only processes the following chunk types: + ``IHDR``, ``PLTE``, ``bKGD``, ``tRNS``, ``gAMA``, ``sBIT``, ``pHYs``. + All other chunk types are ignored. - If the optional `lenient` argument evaluates to True, + If the optional `lenient` argument evaluates to `True`, checksum failures will raise warnings rather than exceptions. """ type, data = self.chunk(lenient=lenient) - method = '_process_' + type + method = '_process_' + type.decode('ascii') m = getattr(self, method, None) if m: m(data) @@ -1791,22 +1671,26 @@ class Reader: check_bitdepth_colortype(self.bitdepth, self.color_type) if self.compression != 0: - raise Error("unknown compression method %d" % self.compression) + raise FormatError( + "Unknown compression method %d" % self.compression) if self.filter != 0: - raise FormatError("Unknown filter method %d," - " see http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters ." - % self.filter) - if self.interlace not in (0,1): - raise FormatError("Unknown interlace method %d," - " see http://www.w3.org/TR/2003/REC-PNG-20031110/#8InterlaceMethods ." - % self.interlace) + raise FormatError( + "Unknown filter method %d," + " see http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters ." + % self.filter) + if self.interlace not in (0, 1): + raise FormatError( + "Unknown interlace method %d, see " + "http://www.w3.org/TR/2003/REC-PNG-20031110/#8InterlaceMethods" + " ." + % self.interlace) # Derived values # http://www.w3.org/TR/PNG/#6Colour-values - colormap = bool(self.color_type & 1) - greyscale = not (self.color_type & 2) + colormap = bool(self.color_type & 1) + greyscale = not(self.color_type & 2) alpha = bool(self.color_type & 4) - color_planes = (3,1)[greyscale or colormap] + color_planes = (3, 1)[greyscale or colormap] planes = color_planes + alpha self.colormap = colormap @@ -1814,7 +1698,7 @@ class Reader: self.alpha = alpha self.color_planes = color_planes self.planes = planes - self.psize = float(self.bitdepth)/float(8) * planes + self.psize = float(self.bitdepth) / float(8) * planes if int(self.psize) == self.psize: self.psize = int(self.psize) self.row_bytes = int(math.ceil(self.width * self.psize)) @@ -1824,7 +1708,7 @@ class Reader: # Stores tRNS chunk if present, and is used to check chunk # ordering constraints. self.trns = None - # Stores sbit chunk if present. + # Stores sBIT chunk if present. self.sbit = None def _process_PLTE(self, data): @@ -1834,8 +1718,8 @@ class Reader: self.plte = data if len(data) % 3 != 0: raise FormatError( - "PLTE chunk's length should be a multiple of 3.") - if len(data) > (2**self.bitdepth)*3: + "PLTE chunk's length should be a multiple of 3.") + if len(data) > (2 ** self.bitdepth) * 3: raise FormatError("PLTE chunk is too long.") if len(data) == 0: raise FormatError("Empty PLTE is not allowed.") @@ -1845,11 +1729,11 @@ class Reader: if self.colormap: if not self.plte: warnings.warn( - "PLTE chunk is required before bKGD chunk.") + "PLTE chunk is required before bKGD chunk.") self.background = struct.unpack('B', data) else: self.background = struct.unpack("!%dH" % self.color_planes, - data) + data) except struct.error: raise FormatError("bKGD chunk has incorrect length.") @@ -1860,15 +1744,15 @@ class Reader: if not self.plte: warnings.warn("PLTE chunk is required before tRNS chunk.") else: - if len(data) > len(self.plte)/3: + if len(data) > len(self.plte) / 3: # Was warning, but promoted to Error as it # would otherwise cause pain later on. raise FormatError("tRNS chunk is too long.") else: if self.alpha: raise FormatError( - "tRNS chunk is not valid with colour type %d." % - self.color_type) + "tRNS chunk is not valid with colour type %d." % + self.color_type) try: self.transparent = \ struct.unpack("!%dH" % self.color_planes, data) @@ -1884,7 +1768,7 @@ class Reader: def _process_sBIT(self, data): self.sbit = data if (self.colormap and len(data) != 3 or - not self.colormap and len(data) != self.planes): + not self.colormap and len(data) != self.planes): raise FormatError("sBIT chunk has incorrect length.") def _process_pHYs(self, data): @@ -1893,17 +1777,19 @@ class Reader: fmt = "!LLB" if len(data) != struct.calcsize(fmt): raise FormatError("pHYs chunk has incorrect length.") - self.x_pixels_per_unit, self.y_pixels_per_unit, unit = struct.unpack(fmt,data) + self.x_pixels_per_unit, self.y_pixels_per_unit, unit = \ + struct.unpack(fmt, data) self.unit_is_meter = bool(unit) def read(self, lenient=False): """ - Read the PNG file and decode it. Returns (`width`, `height`, - `pixels`, `metadata`). + Read the PNG file and decode it. + Returns (`width`, `height`, `rows`, `info`). May use excessive memory. - `pixels` are returned in boxed row flat pixel format. + `rows` is a sequence of rows; + each row is a sequence of values. If the optional `lenient` argument evaluates to True, checksum failures will raise warnings rather than exceptions. @@ -1912,87 +1798,83 @@ class Reader: def iteridat(): """Iterator that yields all the ``IDAT`` chunks as strings.""" while True: - try: - type, data = self.chunk(lenient=lenient) - except ValueError: - raise ChunkError(sys.exc_info()[1].args[0]) - if type == 'IEND': + type, data = self.chunk(lenient=lenient) + if type == b'IEND': # http://www.w3.org/TR/PNG/#11IEND break - if type != 'IDAT': + if type != b'IDAT': continue - # type == 'IDAT' + # type == b'IDAT' # http://www.w3.org/TR/PNG/#11IDAT if self.colormap and not self.plte: warnings.warn("PLTE chunk is required before IDAT chunk") yield data - def iterdecomp(idat): - """Iterator that yields decompressed strings. `idat` should - be an iterator that yields the ``IDAT`` chunk data. - """ - - # Currently, with no max_length parameter to decompress, - # this routine will do one yield per IDAT chunk: Not very - # incremental. - d = zlib.decompressobj() - # Each IDAT chunk is passed to the decompressor, then any - # remaining state is decompressed out. - for data in idat: - # :todo: add a max_length argument here to limit output - # size. - yield array('B', d.decompress(data)) - yield array('B', d.flush()) - self.preamble(lenient=lenient) - raw = iterdecomp(iteridat()) + raw = decompress(iteridat()) + if self.interlace: - raw = array('B', itertools.chain(*raw)) - arraycode = 'BH'[self.bitdepth>8] - # Like :meth:`group` but producing an array.array object for - # each row. - pixels = itertools.imap(lambda *row: array(arraycode, row), - *[iter(self.deinterlace(raw))]*self.width*self.planes) + def rows_from_interlace(): + """Yield each row from an interlaced PNG.""" + # It's important that this iterator doesn't read + # IDAT chunks until it yields the first row. + bs = bytearray(itertools.chain(*raw)) + arraycode = 'BH'[self.bitdepth > 8] + # Like :meth:`group` but + # producing an array.array object for each row. + values = self._deinterlace(bs) + vpr = self.width * self.planes + for i in range(0, len(values), vpr): + row = array(arraycode, values[i:i+vpr]) + yield row + rows = rows_from_interlace() else: - pixels = self.iterboxed(self.iterstraight(raw)) - meta = dict() + rows = self._iter_bytes_to_values(self._iter_straight_packed(raw)) + info = dict() for attr in 'greyscale alpha planes bitdepth interlace'.split(): - meta[attr] = getattr(self, attr) - meta['size'] = (self.width, self.height) + info[attr] = getattr(self, attr) + info['size'] = (self.width, self.height) for attr in 'gamma transparent background'.split(): a = getattr(self, attr, None) if a is not None: - meta[attr] = a + info[attr] = a + if getattr(self, 'x_pixels_per_unit', None): + info['physical'] = Resolution(self.x_pixels_per_unit, + self.y_pixels_per_unit, + self.unit_is_meter) if self.plte: - meta['palette'] = self.palette() - return self.width, self.height, pixels, meta - + info['palette'] = self.palette() + return self.width, self.height, rows, info def read_flat(self): """ - Read a PNG file and decode it into flat row flat pixel format. - Returns (*width*, *height*, *pixels*, *metadata*). + Read a PNG file and decode it into a single array of values. + Returns (*width*, *height*, *values*, *info*). May use excessive memory. - `pixels` are returned in flat row flat pixel format. + `values` is a single array. - See also the :meth:`read` method which returns pixels in the - more stream-friendly boxed row flat pixel format. + The :meth:`read` method is more stream-friendly than this, + because it returns a sequence of rows. """ - x, y, pixel, meta = self.read() - arraycode = 'BH'[meta['bitdepth']>8] + x, y, pixel, info = self.read() + arraycode = 'BH'[info['bitdepth'] > 8] pixel = array(arraycode, itertools.chain(*pixel)) - return x, y, pixel, meta + return x, y, pixel, info def palette(self, alpha='natural'): - """Returns a palette that is a sequence of 3-tuples or 4-tuples, - synthesizing it from the ``PLTE`` and ``tRNS`` chunks. These - chunks should have already been processed (for example, by - calling the :meth:`preamble` method). All the tuples are the - same size: 3-tuples if there is no ``tRNS`` chunk, 4-tuples when - there is a ``tRNS`` chunk. Assumes that the image is colour type + """ + Returns a palette that is a sequence of 3-tuples or 4-tuples, + synthesizing it from the ``PLTE`` and ``tRNS`` chunks. + These chunks should have already been processed (for example, + by calling the :meth:`preamble` method). + All the tuples are the same size: + 3-tuples if there is no ``tRNS`` chunk, + 4-tuples when there is a ``tRNS`` chunk. + + Assumes that the image is colour type 3 and therefore a ``PLTE`` chunk is required. If the `alpha` argument is ``'force'`` then an alpha channel is @@ -2004,45 +1886,52 @@ class Reader: "Required PLTE chunk is missing in colour type 3 image.") plte = group(array('B', self.plte), 3) if self.trns or alpha == 'force': - trns = array('B', self.trns or '') - trns.extend([255]*(len(plte)-len(trns))) - plte = map(operator.add, plte, group(trns, 1)) + trns = array('B', self.trns or []) + trns.extend([255] * (len(plte) - len(trns))) + plte = list(map(operator.add, plte, group(trns, 1))) return plte def asDirect(self): - """Returns the image data as a direct representation of an - ``x * y * planes`` array. This method is intended to remove the - need for callers to deal with palettes and transparency - themselves. Images with a palette (colour type 3) - are converted to RGB or RGBA; images with transparency (a - ``tRNS`` chunk) are converted to LA or RGBA as appropriate. - When returned in this format the pixel values represent the - colour value directly without needing to refer to palettes or - transparency information. + """ + Returns the image data as a direct representation of + an ``x * y * planes`` array. + This removes the need for callers to deal with + palettes and transparency themselves. + Images with a palette (colour type 3) are converted to RGB or RGBA; + images with transparency (a ``tRNS`` chunk) are converted to + LA or RGBA as appropriate. + When returned in this format the pixel values represent + the colour value directly without needing to refer + to palettes or transparency information. Like the :meth:`read` method this method returns a 4-tuple: - (*width*, *height*, *pixels*, *meta*) + (*width*, *height*, *rows*, *info*) - This method normally returns pixel values with the bit depth - they have in the source image, but when the source PNG has an - ``sBIT`` chunk it is inspected and can reduce the bit depth of - the result pixels; pixel values will be reduced according to - the bit depth specified in the ``sBIT`` chunk (PNG nerds should - note a single result bit depth is used for all channels; the - maximum of the ones specified in the ``sBIT`` chunk. An RGB565 - image will be rescaled to 6-bit RGB666). + This method normally returns pixel values with + the bit depth they have in the source image, but + when the source PNG has an ``sBIT`` chunk it is inspected and + can reduce the bit depth of the result pixels; + pixel values will be reduced according to the bit depth + specified in the ``sBIT`` chunk. + PNG nerds should note a single result bit depth is + used for all channels: + the maximum of the ones specified in the ``sBIT`` chunk. + An RGB565 image will be rescaled to 6-bit RGB666. - The *meta* dictionary that is returned reflects the `direct` - format and not the original source image. For example, an RGB - source image with a ``tRNS`` chunk to represent a transparent - colour, will have ``planes=3`` and ``alpha=False`` for the - source image, but the *meta* dictionary returned by this method - will have ``planes=4`` and ``alpha=True`` because an alpha - channel is synthesized and added. + The *info* dictionary that is returned reflects + the `direct` format and not the original source image. + For example, an RGB source image with a ``tRNS`` chunk + to represent a transparent colour, + will start with ``planes=3`` and ``alpha=False`` for the + source image, + but the *info* dictionary returned by this method + will have ``planes=4`` and ``alpha=True`` because + an alpha channel is synthesized and added. - *pixels* is the pixel data in boxed row flat pixel format (just - like the :meth:`read` method). + *rows* is a sequence of rows; + each row being a sequence of values + (like the :meth:`read` method). All the other aspects of the image data are not changed. """ @@ -2053,17 +1942,18 @@ class Reader: if not self.colormap and not self.trns and not self.sbit: return self.read() - x,y,pixels,meta = self.read() + x, y, pixels, info = self.read() if self.colormap: - meta['colormap'] = False - meta['alpha'] = bool(self.trns) - meta['bitdepth'] = 8 - meta['planes'] = 3 + bool(self.trns) - plte = list(self.palette()) + info['colormap'] = False + info['alpha'] = bool(self.trns) + info['bitdepth'] = 8 + info['planes'] = 3 + bool(self.trns) + plte = self.palette() + def iterpal(pixels): for row in pixels: - row = list(map(plte.__getitem__, row)) + row = [plte[x] for x in row] yield array('B', itertools.chain(*row)) pixels = iterpal(pixels) elif self.trns: @@ -2075,11 +1965,12 @@ class Reader: # perhaps go faster (all those 1-tuples!), but I still # wonder whether the code proliferation is worth it) it = self.transparent - maxval = 2**meta['bitdepth']-1 - planes = meta['planes'] - meta['alpha'] = True - meta['planes'] += 1 - typecode = 'BH'[meta['bitdepth']>8] + maxval = 2 ** info['bitdepth'] - 1 + planes = info['planes'] + info['alpha'] = True + info['planes'] += 1 + typecode = 'BH'[info['bitdepth'] > 8] + def itertrns(pixels): for row in pixels: # For each row we group it into pixels, then form a @@ -2090,142 +1981,147 @@ class Reader: row = group(row, planes) opa = map(it.__ne__, row) opa = map(maxval.__mul__, opa) - opa = zip(opa) # convert to 1-tuples - yield array(typecode, - itertools.chain(*map(operator.add, row, opa))) + opa = list(zip(opa)) # convert to 1-tuples + yield array( + typecode, + itertools.chain(*map(operator.add, row, opa))) pixels = itertrns(pixels) targetbitdepth = None if self.sbit: sbit = struct.unpack('%dB' % len(self.sbit), self.sbit) targetbitdepth = max(sbit) - if targetbitdepth > meta['bitdepth']: + if targetbitdepth > info['bitdepth']: raise Error('sBIT chunk %r exceeds bitdepth %d' % - (sbit,self.bitdepth)) + (sbit, self.bitdepth)) if min(sbit) <= 0: raise Error('sBIT chunk %r has a 0-entry' % sbit) - if targetbitdepth == meta['bitdepth']: - targetbitdepth = None if targetbitdepth: - shift = meta['bitdepth'] - targetbitdepth - meta['bitdepth'] = targetbitdepth + shift = info['bitdepth'] - targetbitdepth + info['bitdepth'] = targetbitdepth + def itershift(pixels): for row in pixels: - yield map(shift.__rrshift__, row) + yield [p >> shift for p in row] pixels = itershift(pixels) - return x,y,pixels,meta - - def asFloat(self, maxval=1.0): - """Return image pixels as per :meth:`asDirect` method, but scale - all pixel values to be floating point values between 0.0 and - *maxval*. - """ - - x,y,pixels,info = self.asDirect() - sourcemaxval = 2**info['bitdepth']-1 - del info['bitdepth'] - info['maxval'] = float(maxval) - factor = float(maxval)/float(sourcemaxval) - def iterfloat(): - for row in pixels: - yield map(factor.__mul__, row) - return x,y,iterfloat(),info + return x, y, pixels, info def _as_rescale(self, get, targetbitdepth): """Helper used by :meth:`asRGB8` and :meth:`asRGBA8`.""" - width,height,pixels,meta = get() - maxval = 2**meta['bitdepth'] - 1 + width, height, pixels, info = get() + maxval = 2**info['bitdepth'] - 1 targetmaxval = 2**targetbitdepth - 1 factor = float(targetmaxval) / float(maxval) - meta['bitdepth'] = targetbitdepth + info['bitdepth'] = targetbitdepth + def iterscale(): for row in pixels: - yield map(lambda x: int(round(x*factor)), row) + yield [int(round(x * factor)) for x in row] if maxval == targetmaxval: - return width, height, pixels, meta + return width, height, pixels, info else: - return width, height, iterscale(), meta + return width, height, iterscale(), info def asRGB8(self): - """Return the image data as an RGB pixels with 8-bits per - sample. This is like the :meth:`asRGB` method except that - this method additionally rescales the values so that they - are all between 0 and 255 (8-bit). In the case where the - source image has a bit depth < 8 the transformation preserves - all the information; where the source image has bit depth - > 8, then rescaling to 8-bit values loses precision. No - dithering is performed. Like :meth:`asRGB`, an alpha channel - in the source image will raise an exception. + """ + Return the image data as an RGB pixels with 8-bits per sample. + This is like the :meth:`asRGB` method except that + this method additionally rescales the values so that + they are all between 0 and 255 (8-bit). + In the case where the source image has a bit depth < 8 + the transformation preserves all the information; + where the source image has bit depth > 8, then + rescaling to 8-bit values loses precision. + No dithering is performed. + Like :meth:`asRGB`, + an alpha channel in the source image will raise an exception. This function returns a 4-tuple: - (*width*, *height*, *pixels*, *metadata*). - *width*, *height*, *metadata* are as per the - :meth:`read` method. - - *pixels* is the pixel data in boxed row flat pixel format. + (*width*, *height*, *rows*, *info*). + *width*, *height*, *info* are as per the :meth:`read` method. + + *rows* is the pixel data as a sequence of rows. """ return self._as_rescale(self.asRGB, 8) def asRGBA8(self): - """Return the image data as RGBA pixels with 8-bits per - sample. This method is similar to :meth:`asRGB8` and - :meth:`asRGBA`: The result pixels have an alpha channel, *and* - values are rescaled to the range 0 to 255. The alpha channel is - synthesized if necessary (with a small speed penalty). + """ + Return the image data as RGBA pixels with 8-bits per sample. + This method is similar to :meth:`asRGB8` and :meth:`asRGBA`: + The result pixels have an alpha channel, *and* + values are rescaled to the range 0 to 255. + The alpha channel is synthesized if necessary + (with a small speed penalty). """ return self._as_rescale(self.asRGBA, 8) def asRGB(self): - """Return image as RGB pixels. RGB colour images are passed - through unchanged; greyscales are expanded into RGB - triplets (there is a small speed overhead for doing this). + """ + Return image as RGB pixels. + RGB colour images are passed through unchanged; + greyscales are expanded into RGB triplets + (there is a small speed overhead for doing this). - An alpha channel in the source image will raise an - exception. + An alpha channel in the source image will raise an exception. - The return values are as for the :meth:`read` method - except that the *metadata* reflect the returned pixels, not the - source image. In particular, for this method - ``metadata['greyscale']`` will be ``False``. + The return values are as for the :meth:`read` method except that + the *info* reflect the returned pixels, not the source image. + In particular, + for this method ``info['greyscale']`` will be ``False``. """ - width,height,pixels,meta = self.asDirect() - if meta['alpha']: + width, height, pixels, info = self.asDirect() + if info['alpha']: raise Error("will not convert image with alpha channel to RGB") - if not meta['greyscale']: - return width,height,pixels,meta - meta['greyscale'] = False - typecode = 'BH'[meta['bitdepth'] > 8] + if not info['greyscale']: + return width, height, pixels, info + info['greyscale'] = False + info['planes'] = 3 + + if info['bitdepth'] > 8: + def newarray(): + return array('H', [0]) + else: + def newarray(): + return bytearray([0]) + def iterrgb(): for row in pixels: - a = array(typecode, [0]) * 3 * width + a = newarray() * 3 * width for i in range(3): a[i::3] = row yield a - return width,height,iterrgb(),meta + return width, height, iterrgb(), info def asRGBA(self): - """Return image as RGBA pixels. Greyscales are expanded into - RGB triplets; an alpha channel is synthesized if necessary. - The return values are as for the :meth:`read` method - except that the *metadata* reflect the returned pixels, not the - source image. In particular, for this method - ``metadata['greyscale']`` will be ``False``, and - ``metadata['alpha']`` will be ``True``. + """ + Return image as RGBA pixels. + Greyscales are expanded into RGB triplets; + an alpha channel is synthesized if necessary. + The return values are as for the :meth:`read` method except that + the *info* reflect the returned pixels, not the source image. + In particular, for this method + ``info['greyscale']`` will be ``False``, and + ``info['alpha']`` will be ``True``. """ - width,height,pixels,meta = self.asDirect() - if meta['alpha'] and not meta['greyscale']: - return width,height,pixels,meta - typecode = 'BH'[meta['bitdepth'] > 8] - maxval = 2**meta['bitdepth'] - 1 + width, height, pixels, info = self.asDirect() + if info['alpha'] and not info['greyscale']: + return width, height, pixels, info + typecode = 'BH'[info['bitdepth'] > 8] + maxval = 2**info['bitdepth'] - 1 maxbuffer = struct.pack('=' + typecode, maxval) * 4 * width - def newarray(): - return array(typecode, maxbuffer) - if meta['alpha'] and meta['greyscale']: + if info['bitdepth'] > 8: + def newarray(): + return array('H', maxbuffer) + else: + def newarray(): + return bytearray(maxbuffer) + + if info['alpha'] and info['greyscale']: # LA to RGBA def convert(): for row in pixels: @@ -2233,550 +2129,227 @@ class Reader: # into first three target channels, and A channel # into fourth channel. a = newarray() - pngfilters.convert_la_to_rgba(row, a) + convert_la_to_rgba(row, a) yield a - elif meta['greyscale']: + elif info['greyscale']: # L to RGBA def convert(): for row in pixels: a = newarray() - pngfilters.convert_l_to_rgba(row, a) + convert_l_to_rgba(row, a) yield a else: - assert not meta['alpha'] and not meta['greyscale'] + assert not info['alpha'] and not info['greyscale'] # RGB to RGBA + def convert(): for row in pixels: a = newarray() - pngfilters.convert_rgb_to_rgba(row, a) + convert_rgb_to_rgba(row, a) yield a - meta['alpha'] = True - meta['greyscale'] = False - return width,height,convert(),meta + info['alpha'] = True + info['greyscale'] = False + info['planes'] = 4 + return width, height, convert(), info -def check_bitdepth_colortype(bitdepth, colortype): - """Check that `bitdepth` and `colortype` are both valid, - and specified in a valid combination. Returns if valid, - raise an Exception if not valid. + +def decompress(data_blocks): + """ + `data_blocks` should be an iterable that + yields the compressed data (from the ``IDAT`` chunks). + This yields decompressed byte strings. """ - if bitdepth not in (1,2,4,8,16): + # Currently, with no max_length parameter to decompress, + # this routine will do one yield per IDAT chunk: Not very + # incremental. + d = zlib.decompressobj() + # Each IDAT chunk is passed to the decompressor, then any + # remaining state is decompressed out. + for data in data_blocks: + # :todo: add a max_length argument here to limit output size. + yield bytearray(d.decompress(data)) + yield bytearray(d.flush()) + + +def check_bitdepth_colortype(bitdepth, colortype): + """ + Check that `bitdepth` and `colortype` are both valid, + and specified in a valid combination. + Returns (None) if valid, raise an Exception if not valid. + """ + + if bitdepth not in (1, 2, 4, 8, 16): raise FormatError("invalid bit depth %d" % bitdepth) - if colortype not in (0,2,3,4,6): + if colortype not in (0, 2, 3, 4, 6): raise FormatError("invalid colour type %d" % colortype) # Check indexed (palettized) images have 8 or fewer bits # per pixel; check only indexed or greyscale images have # fewer than 8 bits per pixel. if colortype & 1 and bitdepth > 8: raise FormatError( - "Indexed images (colour type %d) cannot" - " have bitdepth > 8 (bit depth %d)." - " See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ." - % (bitdepth, colortype)) - if bitdepth < 8 and colortype not in (0,3): - raise FormatError("Illegal combination of bit depth (%d)" - " and colour type (%d)." - " See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ." - % (bitdepth, colortype)) + "Indexed images (colour type %d) cannot" + " have bitdepth > 8 (bit depth %d)." + " See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ." + % (bitdepth, colortype)) + if bitdepth < 8 and colortype not in (0, 3): + raise FormatError( + "Illegal combination of bit depth (%d)" + " and colour type (%d)." + " See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ." + % (bitdepth, colortype)) -def isinteger(x): + +def is_natural(x): + """A non-negative integer.""" try: - return int(x) == x + is_integer = int(x) == x except (TypeError, ValueError): return False + return is_integer and x >= 0 -# === Legacy Version Support === +def undo_filter_sub(filter_unit, scanline, previous, result): + """Undo sub filter.""" + + ai = 0 + # Loops starts at index fu. Observe that the initial part + # of the result is already filled in correctly with + # scanline. + for i in range(filter_unit, len(result)): + x = scanline[i] + a = result[ai] + result[i] = (x + a) & 0xff + ai += 1 + + +def undo_filter_up(filter_unit, scanline, previous, result): + """Undo up filter.""" + + for i in range(len(result)): + x = scanline[i] + b = previous[i] + result[i] = (x + b) & 0xff + + +def undo_filter_average(filter_unit, scanline, previous, result): + """Undo up filter.""" + + ai = -filter_unit + for i in range(len(result)): + x = scanline[i] + if ai < 0: + a = 0 + else: + a = result[ai] + b = previous[i] + result[i] = (x + ((a + b) >> 1)) & 0xff + ai += 1 + + +def undo_filter_paeth(filter_unit, scanline, previous, result): + """Undo Paeth filter.""" + + # Also used for ci. + ai = -filter_unit + for i in range(len(result)): + x = scanline[i] + if ai < 0: + a = c = 0 + else: + a = result[ai] + c = previous[ai] + b = previous[i] + p = a + b - c + pa = abs(p - a) + pb = abs(p - b) + pc = abs(p - c) + if pa <= pb and pa <= pc: + pr = a + elif pb <= pc: + pr = b + else: + pr = c + result[i] = (x + pr) & 0xff + ai += 1 + + +def convert_la_to_rgba(row, result): + for i in range(3): + result[i::4] = row[0::2] + result[3::4] = row[1::2] + + +def convert_l_to_rgba(row, result): + """ + Convert a grayscale image to RGBA. + This method assumes the alpha channel in result is + already correctly initialized. + """ + for i in range(3): + result[i::4] = row + + +def convert_rgb_to_rgba(row, result): + """ + Convert an RGB image to RGBA. + This method assumes the alpha channel in result is + already correctly initialized. + """ + for i in range(3): + result[i::4] = row[i::3] + + +# Only reason to include this in this module is that +# several utilities need it, and it is small. +def binary_stdin(): + """ + A sys.stdin that returns bytes. + """ -# :pyver:old: PyPNG works on Python versions 2.3 and 2.2, but not -# without some awkward problems. Really PyPNG works on Python 2.4 (and -# above); it works on Pythons 2.3 and 2.2 by virtue of fixing up -# problems here. It's a bit ugly (which is why it's hidden down here). -# -# Generally the strategy is one of pretending that we're running on -# Python 2.4 (or above), and patching up the library support on earlier -# versions so that it looks enough like Python 2.4. When it comes to -# Python 2.2 there is one thing we cannot patch: extended slices -# http://www.python.org/doc/2.3/whatsnew/section-slices.html. -# Instead we simply declare that features that are implemented using -# extended slices will not work on Python 2.2. -# -# In order to work on Python 2.3 we fix up a recurring annoyance involving -# the array type. In Python 2.3 an array cannot be initialised with an -# array, and it cannot be extended with a list (or other sequence). -# Both of those are repeated issues in the code. Whilst I would not -# normally tolerate this sort of behaviour, here we "shim" a replacement -# for array into place (and hope no-one notices). You never read this. -# -# In an amusing case of warty hacks on top of warty hacks... the array -# shimming we try and do only works on Python 2.3 and above (you can't -# subclass array.array in Python 2.2). So to get it working on Python -# 2.2 we go for something much simpler and (probably) way slower. -try: - array('B').extend([]) - array('B', array('B')) -# :todo:(drj) Check that TypeError is correct for Python 2.3 -except TypeError: - # Expect to get here on Python 2.3 try: - class _array_shim(array): - true_array = array - def __new__(cls, typecode, init=None): - super_new = super(_array_shim, cls).__new__ - it = super_new(cls, typecode) - if init is None: - return it - it.extend(init) - return it - def extend(self, extension): - super_extend = super(_array_shim, self).extend - if isinstance(extension, self.true_array): - return super_extend(extension) - if not isinstance(extension, (list, str)): - # Convert to list. Allows iterators to work. - extension = list(extension) - return super_extend(self.true_array(self.typecode, extension)) - array = _array_shim - except TypeError: - # Expect to get here on Python 2.2 - def array(typecode, init=()): - if type(init) == str: - return map(ord, init) - return list(init) - -# Further hacks to get it limping along on Python 2.2 -try: - enumerate -except NameError: - def enumerate(seq): - i=0 - for x in seq: - yield i,x - i += 1 - -try: - reversed -except NameError: - def reversed(l): - l = list(l) - l.reverse() - for x in l: - yield x - -try: - itertools -except NameError: - class _dummy_itertools: - pass - itertools = _dummy_itertools() - def _itertools_imap(f, seq): - for x in seq: - yield f(x) - itertools.imap = _itertools_imap - def _itertools_chain(*iterables): - for it in iterables: - for element in it: - yield element - itertools.chain = _itertools_chain + return sys.stdin.buffer + except AttributeError: + # Probably Python 2, where bytes are strings. + return sys.stdin -# === Support for users without Cython === - -try: - pngfilters -except NameError: - class pngfilters(object): - def undo_filter_sub(filter_unit, scanline, previous, result): - """Undo sub filter.""" - - ai = 0 - # Loops starts at index fu. Observe that the initial part - # of the result is already filled in correctly with - # scanline. - for i in range(filter_unit, len(result)): - x = scanline[i] - a = result[ai] - result[i] = (x + a) & 0xff - ai += 1 - undo_filter_sub = staticmethod(undo_filter_sub) - - def undo_filter_up(filter_unit, scanline, previous, result): - """Undo up filter.""" - - for i in range(len(result)): - x = scanline[i] - b = previous[i] - result[i] = (x + b) & 0xff - undo_filter_up = staticmethod(undo_filter_up) - - def undo_filter_average(filter_unit, scanline, previous, result): - """Undo up filter.""" - - ai = -filter_unit - for i in range(len(result)): - x = scanline[i] - if ai < 0: - a = 0 - else: - a = result[ai] - b = previous[i] - result[i] = (x + ((a + b) >> 1)) & 0xff - ai += 1 - undo_filter_average = staticmethod(undo_filter_average) - - def undo_filter_paeth(filter_unit, scanline, previous, result): - """Undo Paeth filter.""" - - # Also used for ci. - ai = -filter_unit - for i in range(len(result)): - x = scanline[i] - if ai < 0: - a = c = 0 - else: - a = result[ai] - c = previous[ai] - b = previous[i] - p = a + b - c - pa = abs(p - a) - pb = abs(p - b) - pc = abs(p - c) - if pa <= pb and pa <= pc: - pr = a - elif pb <= pc: - pr = b - else: - pr = c - result[i] = (x + pr) & 0xff - ai += 1 - undo_filter_paeth = staticmethod(undo_filter_paeth) - - def convert_la_to_rgba(row, result): - for i in range(3): - result[i::4] = row[0::2] - result[3::4] = row[1::2] - convert_la_to_rgba = staticmethod(convert_la_to_rgba) - - def convert_l_to_rgba(row, result): - """Convert a grayscale image to RGBA. This method assumes - the alpha channel in result is already correctly - initialized. - """ - for i in range(3): - result[i::4] = row - convert_l_to_rgba = staticmethod(convert_l_to_rgba) - - def convert_rgb_to_rgba(row, result): - """Convert an RGB image to RGBA. This method assumes the - alpha channel in result is already correctly initialized. - """ - for i in range(3): - result[i::4] = row[i::3] - convert_rgb_to_rgba = staticmethod(convert_rgb_to_rgba) - - -# === Command Line Support === - -def read_pam_header(infile): +def binary_stdout(): """ - Read (the rest of a) PAM header. `infile` should be positioned - immediately after the initial 'P7' line (at the beginning of the - second line). Returns are as for `read_pnm_header`. - """ - - # Unlike PBM, PGM, and PPM, we can read the header a line at a time. - header = dict() - while True: - l = infile.readline().strip() - if l == strtobytes('ENDHDR'): - break - if not l: - raise EOFError('PAM ended prematurely') - if l[0] == strtobytes('#'): - continue - l = l.split(None, 1) - if l[0] not in header: - header[l[0]] = l[1] - else: - header[l[0]] += strtobytes(' ') + l[1] - - required = ['WIDTH', 'HEIGHT', 'DEPTH', 'MAXVAL'] - required = [strtobytes(x) for x in required] - WIDTH,HEIGHT,DEPTH,MAXVAL = required - present = [x for x in required if x in header] - if len(present) != len(required): - raise Error('PAM file must specify WIDTH, HEIGHT, DEPTH, and MAXVAL') - width = int(header[WIDTH]) - height = int(header[HEIGHT]) - depth = int(header[DEPTH]) - maxval = int(header[MAXVAL]) - if (width <= 0 or - height <= 0 or - depth <= 0 or - maxval <= 0): - raise Error( - 'WIDTH, HEIGHT, DEPTH, MAXVAL must all be positive integers') - return 'P7', width, height, depth, maxval - -def read_pnm_header(infile, supported=('P5','P6')): - """ - Read a PNM header, returning (format,width,height,depth,maxval). - `width` and `height` are in pixels. `depth` is the number of - channels in the image; for PBM and PGM it is synthesized as 1, for - PPM as 3; for PAM images it is read from the header. `maxval` is - synthesized (as 1) for PBM images. + A sys.stdout that accepts bytes. """ - # Generally, see http://netpbm.sourceforge.net/doc/ppm.html - # and http://netpbm.sourceforge.net/doc/pam.html + # First there is a Python3 issue. + try: + stdout = sys.stdout.buffer + except AttributeError: + # Probably Python 2, where bytes are strings. + stdout = sys.stdout - supported = [strtobytes(x) for x in supported] - - # Technically 'P7' must be followed by a newline, so by using - # rstrip() we are being liberal in what we accept. I think this - # is acceptable. - type = infile.read(3).rstrip() - if type not in supported: - raise NotImplementedError('file format %s not supported' % type) - if type == strtobytes('P7'): - # PAM header parsing is completely different. - return read_pam_header(infile) - # Expected number of tokens in header (3 for P4, 4 for P6) - expected = 4 - pbm = ('P1', 'P4') - if type in pbm: - expected = 3 - header = [type] - - # We have to read the rest of the header byte by byte because the - # final whitespace character (immediately following the MAXVAL in - # the case of P6) may not be a newline. Of course all PNM files in - # the wild use a newline at this point, so it's tempting to use - # readline; but it would be wrong. - def getc(): - c = infile.read(1) - if not c: - raise Error('premature EOF reading PNM header') - return c - - c = getc() - while True: - # Skip whitespace that precedes a token. - while c.isspace(): - c = getc() - # Skip comments. - while c == '#': - while c not in '\n\r': - c = getc() - if not c.isdigit(): - raise Error('unexpected character %s found in header' % c) - # According to the specification it is legal to have comments - # that appear in the middle of a token. - # This is bonkers; I've never seen it; and it's a bit awkward to - # code good lexers in Python (no goto). So we break on such - # cases. - token = strtobytes('') - while c.isdigit(): - token += c - c = getc() - # Slight hack. All "tokens" are decimal integers, so convert - # them here. - header.append(int(token)) - if len(header) == expected: - break - # Skip comments (again) - while c == '#': - while c not in '\n\r': - c = getc() - if not c.isspace(): - raise Error('expected header to end with whitespace, not %s' % c) - - if type in pbm: - # synthesize a MAXVAL - header.append(1) - depth = (1,3)[type == strtobytes('P6')] - return header[0], header[1], header[2], depth, header[3] - -def write_pnm(file, width, height, pixels, meta): - """Write a Netpbm PNM/PAM file. - """ - - bitdepth = meta['bitdepth'] - maxval = 2**bitdepth - 1 - # Rudely, the number of image planes can be used to determine - # whether we are L (PGM), LA (PAM), RGB (PPM), or RGBA (PAM). - planes = meta['planes'] - # Can be an assert as long as we assume that pixels and meta came - # from a PNG file. - assert planes in (1,2,3,4) - if planes in (1,3): - if 1 == planes: - # PGM - # Could generate PBM if maxval is 1, but we don't (for one - # thing, we'd have to convert the data, not just blat it - # out). - fmt = 'P5' - else: - # PPM - fmt = 'P6' - header = '%s %d %d %d\n' % (fmt, width, height, maxval) - if planes in (2,4): - # PAM - # See http://netpbm.sourceforge.net/doc/pam.html - if 2 == planes: - tupltype = 'GRAYSCALE_ALPHA' - else: - tupltype = 'RGB_ALPHA' - header = ('P7\nWIDTH %d\nHEIGHT %d\nDEPTH %d\nMAXVAL %d\n' - 'TUPLTYPE %s\nENDHDR\n' % - (width, height, planes, maxval, tupltype)) - file.write(header.encode('ascii')) - # Values per row - vpr = planes * width - # struct format - fmt = '>%d' % vpr - if maxval > 0xff: - fmt = fmt + 'H' - else: - fmt = fmt + 'B' - for row in pixels: - file.write(struct.pack(fmt, *row)) - file.flush() - -def color_triple(color): - """ - Convert a command line colour value to a RGB triple of integers. - FIXME: Somewhere we need support for greyscale backgrounds etc. - """ - if color.startswith('#') and len(color) == 4: - return (int(color[1], 16), - int(color[2], 16), - int(color[3], 16)) - if color.startswith('#') and len(color) == 7: - return (int(color[1:3], 16), - int(color[3:5], 16), - int(color[5:7], 16)) - elif color.startswith('#') and len(color) == 13: - return (int(color[1:5], 16), - int(color[5:9], 16), - int(color[9:13], 16)) - -def _add_common_options(parser): - """Call *parser.add_option* for each of the options that are - common between this PNG--PNM conversion tool and the gen - tool. - """ - parser.add_option("-i", "--interlace", - default=False, action="store_true", - help="create an interlaced PNG file (Adam7)") - parser.add_option("-t", "--transparent", - action="store", type="string", metavar="#RRGGBB", - help="mark the specified colour as transparent") - parser.add_option("-b", "--background", - action="store", type="string", metavar="#RRGGBB", - help="save the specified background colour") - parser.add_option("-g", "--gamma", - action="store", type="float", metavar="value", - help="save the specified gamma value") - parser.add_option("-c", "--compression", - action="store", type="int", metavar="level", - help="zlib compression level (0-9)") - return parser - -def _main(argv): - """ - Run the PNG encoder with options from the command line. - """ - - # Parse command line arguments - from optparse import OptionParser - version = '%prog ' + __version__ - parser = OptionParser(version=version) - parser.set_usage("%prog [options] [imagefile]") - parser.add_option('-r', '--read-png', default=False, - action='store_true', - help='Read PNG, write PNM') - parser.add_option("-a", "--alpha", - action="store", type="string", metavar="pgmfile", - help="alpha channel transparency (RGBA)") - _add_common_options(parser) - - (options, args) = parser.parse_args(args=argv[1:]) - - # Convert options - if options.transparent is not None: - options.transparent = color_triple(options.transparent) - if options.background is not None: - options.background = color_triple(options.background) - - # Prepare input and output files - if len(args) == 0: - infilename = '-' - infile = sys.stdin - elif len(args) == 1: - infilename = args[0] - infile = open(infilename, 'rb') - else: - parser.error("more than one input file") - outfile = sys.stdout + # On Windows the C runtime file orientation needs changing. if sys.platform == "win32": - import msvcrt, os + import msvcrt + import os msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY) - if options.read_png: - # Encode PNG to PPM - png = Reader(file=infile) - width,height,pixels,meta = png.asDirect() - write_pnm(outfile, width, height, pixels, meta) - else: - # Encode PNM to PNG - format, width, height, depth, maxval = \ - read_pnm_header(infile, ('P5','P6','P7')) - # When it comes to the variety of input formats, we do something - # rather rude. Observe that L, LA, RGB, RGBA are the 4 colour - # types supported by PNG and that they correspond to 1, 2, 3, 4 - # channels respectively. So we use the number of channels in - # the source image to determine which one we have. We do not - # care about TUPLTYPE. - greyscale = depth <= 2 - pamalpha = depth in (2,4) - supported = map(lambda x: 2**x-1, range(1,17)) - try: - mi = supported.index(maxval) - except ValueError: - raise NotImplementedError( - 'your maxval (%s) not in supported list %s' % - (maxval, str(supported))) - bitdepth = mi+1 - writer = Writer(width, height, - greyscale=greyscale, - bitdepth=bitdepth, - interlace=options.interlace, - transparent=options.transparent, - background=options.background, - alpha=bool(pamalpha or options.alpha), - gamma=options.gamma, - compression=options.compression) - if options.alpha: - pgmfile = open(options.alpha, 'rb') - format, awidth, aheight, adepth, amaxval = \ - read_pnm_header(pgmfile, 'P5') - if amaxval != '255': - raise NotImplementedError( - 'maxval %s not supported for alpha channel' % amaxval) - if (awidth, aheight) != (width, height): - raise ValueError("alpha channel image size mismatch" - " (%s has %sx%s but %s has %sx%s)" - % (infilename, width, height, - options.alpha, awidth, aheight)) - writer.convert_ppm_and_pgm(infile, pgmfile, outfile) - else: - writer.convert_pnm(infile, outfile) + return stdout + + +def cli_open(path): + if path == "-": + return binary_stdin() + return open(path, "rb") + + +def main(argv): + """ + Run command line PNG. + """ + print("What should the command line tool do?", file=sys.stderr) if __name__ == '__main__': try: - _main(sys.argv) - except Error: - e = sys.exc_info()[1] + main(sys.argv) + except Error as e: print(e, file=sys.stderr)