
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 and you have a reasonably
up-to-date set of tools, running ./autogen.sh before running ./configure
may fix the problem.  You can also run the individual commands in
autogen.sh with the --force option, if supported by your version of
the tools.  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
    ./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 you want to use "cmake" (see www.cmake.org), type

   cmake . -DCMAKE_INSTALL_PREFIX=/path
   make
   make install

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.

You can rename the directories that you downloaded (they
might be called "libpng-x.y.z" or "libpngNN" and "zlib-1.2.5"
or "zlib125") 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
             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 pngconf.h 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".

If you encounter a compiler error message complaining about the
lines

      __png.h__ already includes setjmp.h;
      __dont__ include it again.;

this means you have compiled another module that includes setjmp.h,
which is hazardous because the two modules might not include exactly
the same setjmp.h.  If you are sure that you know what you are doing
and that they are exactly the same, then you can comment out or
delete the two lines.  Better yet, use the cexcept interface
instead, as demonstrated in contrib/visupng of the libpng distribution.

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