SlackBuildsOrg/libraries/libpng-legacy12

libpng-legacy12 (old PNG library for compatibility with old software)

PNG (Portable Network Graphics) is an extensible file format for the
lossless, portable, well-compressed storage of raster images.

This build provides libpng12.so, occasionally needed for running older
binary-only software. It can safely be installed without conflicting
with Slackware's own libpng (which is version 1.6).

Rather than compiling libpng-1.2, this build simply repackages the
latest official binary from Slackware 14.1's patches/.

If you're looking for libpng-1.4, it's already provided in Slackware's
aaa_libraries package (as libpng14.so).