Installing libpng

On Unix/Linux and similar systems, you can simply type

    ./configure [--prefix=/path]
    make check
    make install

and ignore the rest of this document.

If configure does not work on your system, or if you have a need to
change configure.ac or Makefile.am, and you have a reasonably
up-to-date set of tools, running ./autogen.sh in a git clone before
running ./configure may fix the problem.  To be really sure that you
aren't using any of the included pre-built scripts, you can do this:

    ./configure --enable-maintainer-mode
    make maintainer-clean
    ./autogen.sh --maintainer --clean
    ./autogen.sh --maintainer
    ./configure [--prefix=/path] [other options]
    make
    make install
    make check

Instead, you can use one of the custom-built makefiles in the
"scripts" directory

    cp scripts/makefile.system makefile
    make test
    make install

The files that are presently available in the scripts directory
are listed and described in scripts/README.txt.

Or you can use one of the "projects" in the "projects" directory.

Before installing libpng, you must first install zlib, if it
is not already on your system.  zlib can usually be found
wherever you got libpng.  zlib can be placed in another directory,
at the same level as libpng.

If your system already has a preinstalled zlib you will still need
to have access to the zlib.h and zconf.h include files that
correspond to the version of zlib that's installed.

If you wish to test with a particular zlib that is not first in the
standard library search path, put ZLIBLIB, ZLIBINC, CPPFLAGS, LDFLAGS,
and LD_LIBRARY_PATH in your environment before running "make test"
or "make distcheck":

ZLIBLIB=/path/to/lib export ZLIBLIB
ZLIBINC=/path/to/include export ZLIBINC
CPPFLAGS="-I$ZLIBINC" export CPPFLAGS
LDFLAGS="-L$ZLIBLIB" export LDFLAGS
LD_LIBRARY_PATH="$ZLIBLIB:$LD_LIBRARY_PATH" export LD_LIBRARY_PATH

If you are using one of the makefile scripts, put ZLIBLIB and ZLIBINC
in your environment and type "make ZLIBLIB=$ZLIBLIB ZLIBINC=$ZLIBINC test".

If you want to use "cmake" (see www.cmake.org), type

   cmake . -DCMAKE_INSTALL_PREFIX=/path
   make
   make install

You can rename the directories that you downloaded (they
might be called "libpng-x.y.z" or "libpngNN" and "zlib-1.2.7"
or "zlib127") so that you have directories called "zlib" and "libpng".

Your directory structure should look like this:

   ..       (the parent directory)
      libpng  (this directory)
          INSTALL (this file)
          README
          *.h
          *.c
          CMakeLists.txt    =>  "cmake" script
          configuration files:
             configure.ac, configure, Makefile.am, Makefile.in,
             autogen.sh, config.guess, ltmain.sh, missing, libpng.pc.in,
             libpng-config.in, aclocal.m4, config.h.in, config.sub,
             depcomp, install-sh, mkinstalldirs, test-pngtest.sh
          contrib
             gregbook
             libtests
             pngminim
             pngminus
             pngsuite
             visupng
          projects
             visualc71
             vstudio
          scripts
             makefile.*
             *.def (module definition files)
             etc.
          pngtest.png
          etc.
      zlib
          README
          *.h
          *.c
          contrib
          etc.

If the line endings in the files look funny, you may wish to get the other
distribution of libpng.  It is available in both tar.gz (UNIX style line
endings) and zip (DOS style line endings) formats.

If you are building libpng with MSVC, you can enter the
libpng projects\visualc6 or visualc71 directory and follow the instructions
in README.txt.

Otherwise enter the zlib directory and follow the instructions in zlib/README,
then come back here and run "configure" or choose the appropriate
makefile.sys in the scripts directory.

Copy the file (or files) that you need from the
scripts directory into this directory, for example

   MSDOS example: copy scripts\makefile.msc makefile
   UNIX example:    cp scripts/makefile.std makefile

Read the makefile to see if you need to change any source or
target directories to match your preferences.

Then read pnglibconf.dfa to see if you want to make any configuration
changes.

Then just run "make" which will create the libpng library in
this directory and "make test" which will run a quick test that reads
the "pngtest.png" file and writes a "pngout.png" file that should be
identical to it.  Look for "9782 zero samples" in the output of the
test.  For more confidence, you can run another test by typing
"pngtest pngnow.png" and looking for "289 zero samples" in the output.
Also, you can run "pngtest -m contrib/pngsuite/*.png" and compare
your output with the result shown in contrib/pngsuite/README.

Most of the makefiles will allow you to run "make install" to
put the library in its final resting place (if you want to
do that, run "make install" in the zlib directory first if necessary).
Some also allow you to run "make test-installed" after you have
run "make install".

Further information can be found in the README and libpng-manual.txt
files, in the individual makefiles, in png.h, and the manual pages
libpng.3 and png.5.