libpng: Bitmap image support

Description

libpng is the official PNG reference library. It supports almost all PNG features, is extensible, and has been extensively tested for over 13 years. The home site for development versions (i.e., may be buggy or subject to change or include experimental features) is http://libpng.sourceforge.net/, and the place to go for questions about the library is the png-mng-implement mailing list.

Website: http://www.libpng.org/pub/png/libpng.html

Dependencies

This spkg depends on:

  • libz

Special Update/Build Instructions

  • On old versions of Darwin, the symbolic links libpng.* created by libpng16 may interfere with a system-wide libPng.dylib.

    – the following is very likely to be obsolete in 2014 —

    This system-wide library is likely to be a different version and on top of that, the symbols exported there are prefixed with “_cg” (for “Core Graphics”). So even if by chance the functionalities of the two libraries were interchangeable, libraries or applications looking for one and being presented the other won’t find the symbols they expect. Note the uppercase “P” which could prevent this conflict; unfortunately, the default filesystem used by Apple is case-insensitive.

    Note there would be no problem if the system-wide library was not looked for when Sage is being built or run, but that’s not the case either; it is at least looked for by the “ImageIO” framework:

    • when Python is built with Mac OS extensions, fixed in #4008;

    • when Mercurial is built because it uses $EDITOR, cf. #4678;

    • when R is built and it finds -lpng, cf. #4409 and #11696.

    – this is no longer done, as of #27186 —

    As not all of these problems are easily dealt with and new ones may arise, we chose to delete the $SAGE_LOCAL/lib/libpng.* symlinks. Therefore, some packages like Tachyon, which by default look for -lpng are patched to look for -lpng16 instead.

Type

standard

Version Information

package-version.txt:

1.6.29.p1

Equivalent System Packages

conda:

$ conda install libpng-devel

freebsd:

$ sudo pkg install libpng-devel

homebrew:

$ brew install libpng-devel

macports: install the following packages: libpng-devel opensuse:

$ sudo zypper install libpng-devel

slackware:

$ sudo slackpkg install libpng-devel

void:

$ sudo xbps-install  libpng-devel

See https://repology.org/project/libpng-devel/versions

If the system package is installed, ./configure will check whether it can be used.