-Before installing libpng, you must first install zlib. zlib
-can usually be found wherever you got libpng. zlib can be
-placed in another directory, at the same level as libpng.
-Note that your system might already have a preinstalled
-zlib, but 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.
+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