Installing libpng

Contents

   I. Simple installation

  II. Rebuilding the configure scripts

 III. Using scripts/makefile*

  IV. Using cmake

   V. Directory structure

  VI. Building with project files

 VII. Building with makefiles

VIII. Configuring libpng for 16-bit platforms

  IX. Configuring for DOS

   X. Configuring for Medium Model

  XI. Prepending a prefix to exported symbols

 XII. Configuring for compiler xxx:

XIII. Removing unwanted object code

 XIV. Changes to the build and configuration of libpng in libpng-1.5.x

  XV. Setjmp/longjmp issues

 XVI. Other sources of information about libpng

I. Simple installation

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

    ./configure [--prefix=/path]

    make check

    make install

and ignore the rest of this document.  "/path" is the path to the directory

where you want to install the libpng "lib", "include", and "bin"

subdirectories.

If you downloaded a GIT clone, you will need to run ./autogen.sh before

running ./configure, to create "configure" and "Makefile.in" which are

not included in the GIT repository.

Note that "configure" is only included in the "*.tar" distributions and not

in the "*.zip" or "*.7z" distributions. If you downloaded one of those

distributions, see "Building with project files" or "Building with makefiles",

below.

II. Rebuilding the configure scripts

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

III. Using scripts/makefile*

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

"scripts" directory

    cp scripts/pnglibconf.h.prebuilt pnglibconf.h

    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; otherwise go to http://zlib.net.  You can place

zlib in in the same directory as libpng or in another directory.

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".

IV. Using cmake

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

   cmake . -DCMAKE_INSTALL_PREFIX=/path

   make

   make install

As when using the simple configure method described above, "/path" points to

the installation directory where you want to put the libpng "lib", "include",

and "bin" subdirectories.

V. Directory structure

You can rename the directories that you downloaded (they

might be called "libpng-x.y.z" or "libpngNN" and "zlib-1.2.8"

or "zlib128") 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  => libpng source files

          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

             arm-neon, conftest, examples, gregbook, libtests, pngminim,

             pngminus, pngsuite, tools, visupng

          projects

             cbuilder5, owatcom, visualc71, vstudio, xcode

          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.

VI. Building with project files

If you are building libpng with MSVC, you can enter the

libpng projects\visualc71 or vstudio 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.

VII. Building with makefiles

Copy the file (or files) that you need from the

scripts directory into this directory, for example

   MSDOS example: copy scripts\makefile.msc makefile

                  copy scripts\pnglibconf.h.prebuilt pnglibconf.h

   UNIX example:  cp scripts/makefile.std makefile

                  cp scripts/pnglibconf.h.prebuilt pnglibconf.h

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".

VIII. Configuring libpng for 16-bit platforms

You will want to look into zconf.h to tell zlib (and thus libpng) that

it cannot allocate more than 64K at a time.  Even if you can, the memory

won't be accessible.  So limit zlib and libpng to 64K by defining MAXSEG_64K.

IX. Configuring for DOS

For DOS users who only have access to the lower 640K, you will

have to limit zlib's memory usage via a png_set_compression_mem_level()

call.  See zlib.h or zconf.h in the zlib library for more information.

X. Configuring for Medium Model

Libpng's support for medium model has been tested on most of the popular

compilers.  Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets

defined, and FAR gets defined to far in pngconf.h, and you should be

all set.  Everything in the library (except for zlib's structure) is

expecting far data.  You must use the typedefs with the p or pp on

the end for pointers (or at least look at them and be careful).  Make

note that the rows of data are defined as png_bytepp, which is

an "unsigned char far * far *".

XI. Prepending a prefix to exported symbols

Starting with libpng-1.6.0, you can configure libpng (when using the

"configure" script) to prefix all exported symbols by means of the

configuration option "--with-libpng-prefix=FOO_", where FOO_ can be any

string beginning with a letter and containing only uppercase

and lowercase letters, digits, and the underscore (i.e., a C language

identifier).  This creates a set of macros in pnglibconf.h, so this is

transparent to applications; their function calls get transformed by

the macros to use the modified names.

XII. Configuring for compiler xxx:

All includes for libpng are in pngconf.h.  If you need to add, change

or delete an include, this is the place to do it.

The includes that are not needed outside libpng are placed in pngpriv.h,

which is only used by the routines inside libpng itself.

The files in libpng proper only include pngpriv.h and png.h, which

in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.

As of libpng-1.5.0, pngpriv.h also includes three other private header

files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material

that previously appeared in the public headers.

XIII. Removing unwanted object code

There are a bunch of #define's in pngconf.h that control what parts of

libpng are compiled.  All the defines end in _SUPPORTED.  If you are

never going to use a capability, you can change the #define to #undef

before recompiling libpng and save yourself code and data space, or

you can turn off individual capabilities with defines that begin with

PNG_NO_.

In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead.

You can also turn all of the transforms and ancillary chunk capabilities

off en masse with compiler directives that define

PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,

or all four, along with directives to turn on any of the capabilities that

you do want.  The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the

extra transformations but still leave the library fully capable of reading

and writing PNG files with all known public chunks. Use of the

PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library

that is incapable of reading or writing ancillary chunks.  If you are

not using the progressive reading capability, you can turn that off

with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING

capability, which you'll still have).

All the reading and writing specific code are in separate files, so the

linker should only grab the files it needs.  However, if you want to

make sure, or if you are building a stand alone library, all the

reading files start with "pngr" and all the writing files start with "pngw".

The files that don't match either (like png.c, pngtrans.c, etc.)

are used for both reading and writing, and always need to be included.

The progressive reader is in pngpread.c

If you are creating or distributing a dynamically linked library (a .so

or DLL file), you should not remove or disable any parts of the library,

as this will cause applications linked with different versions of the

library to fail if they call functions not available in your library.

The size of the library itself should not be an issue, because only

those sections that are actually used will be loaded into memory.

XIV. Changes to the build and configuration of libpng in libpng-1.5.x

Details of internal changes to the library code can be found in the CHANGES

file and in the GIT repository logs.  These will be of no concern to the vast

majority of library users or builders; however, the few who configure libpng

to a non-default feature set may need to change how this is done.

There should be no need for library builders to alter build scripts if

these use the distributed build support - configure or the makefiles -

however, users of the makefiles may care to update their build scripts

to build pnglibconf.h where the corresponding makefile does not do so.

Building libpng with a non-default configuration has changed completely.

The old method using pngusr.h should still work correctly even though the

way pngusr.h is used in the build has been changed; however, library

builders will probably want to examine the changes to take advantage of

new capabilities and to simplify their build system.

A. Specific changes to library configuration capabilities

The exact mechanism used to control attributes of API functions has

changed.  A single set of operating system independent macro definitions

is used and operating system specific directives are defined in

pnglibconf.h

As part of this the mechanism used to choose procedure call standards on

those systems that allow a choice has been changed.  At present this only

affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems

running on Intel processors.  As before, PNGAPI is defined where required

to control the exported API functions; however, two new macros, PNGCBAPI

and PNGCAPI, are used instead for callback functions (PNGCBAPI) and

(PNGCAPI) for functions that must match a C library prototype (currently

only png_longjmp_ptr, which must match the C longjmp function.)  The new

approach is documented in pngconf.h

Despite these changes, libpng 1.5.0 only supports the native C function

calling standard on those platforms tested so far (__cdecl on Microsoft

Windows).  This is because the support requirements for alternative

calling conventions seem to no longer exist.  Developers who find it

necessary to set PNG_API_RULE to 1 should advise the mailing list

(png-mng-implement) of this and library builders who use Openwatcom and

therefore set PNG_API_RULE to 2 should also contact the mailing list.

B. Changes to the configuration mechanism

Prior to libpng-1.5.0 library builders who needed to configure libpng

had either to modify the exported pngconf.h header file to add system

specific configuration or had to write feature selection macros into

pngusr.h and cause this to be included into pngconf.h by defining

PNG_USER_CONFIG. The latter mechanism had the disadvantage that an

application built without PNG_USER_CONFIG defined would see the

unmodified, default, libpng API and thus would probably fail to link.

These mechanisms still work in the configure build and in any makefile

build that builds pnglibconf.h, although the feature selection macros

have changed somewhat as described above.  In 1.5.0, however, pngusr.h is

processed only once, at the time the exported header file pnglibconf.h is

built.  pngconf.h no longer includes pngusr.h; therefore, pngusr.h is ignored

after the build of pnglibconf.h and it is never included in an application

build.

The formerly used alternative of adding a list of feature macros to the

CPPFLAGS setting in the build also still works; however, the macros will be

copied to pnglibconf.h and this may produce macro redefinition warnings

when the individual C files are compiled.

All configuration now only works if pnglibconf.h is built from

scripts/pnglibconf.dfa.  This requires the program awk.  Brian Kernighan

(the original author of awk) maintains C source code of that awk and this

and all known later implementations (often called by subtly different

names - nawk and gawk for example) are adequate to build pnglibconf.h.

The Sun Microsystems (now Oracle) program 'awk' is an earlier version

and does not work; this may also apply to other systems that have a

functioning awk called 'nawk'.

Configuration options are now documented in scripts/pnglibconf.dfa.  This

file also includes dependency information that ensures a configuration is

consistent; that is, if a feature is switched off, dependent features are

also switched off.  As a recommended alternative to using feature macros in

pngusr.h a system builder may also define equivalent options in pngusr.dfa

(or, indeed, any file) and add that to the configuration by setting

DFA_XTRA to the file name.  The makefiles in contrib/pngminim illustrate

how to do this, and also illustrate a case where pngusr.h is still required.

After you have built libpng, the definitions that were recorded in

pnglibconf.h are available to your application (pnglibconf.h is included

in png.h and gets installed alongside png.h and pngconf.h in your

$PREFIX/include directory).  Do not edit pnglibconf.h after you have built

libpng, because than the settings would not accurately reflect the settings

that were used to build libpng.

XV. Setjmp/longjmp issues

Libpng uses setjmp()/longjmp() for error handling.  Unfortunately setjmp()

is known to be not thread-safe on some platforms and we don't know of

any platform where it is guaranteed to be thread-safe.  Therefore, if

your application is going to be using multiple threads, you should

configure libpng with PNG_NO_SETJMP in your pngusr.dfa file, with

-DPNG_NO_SETJMP on your compile line, or with

  #undef PNG_SETJMP_SUPPORTED

in your pnglibconf.h or pngusr.h.

Starting with libpng-1.6.0, the library included a "simplified API".

This requires setjmp/longjmp, so you must either build the library

with PNG_SETJMP_SUPPORTED defined, or with PNG_SIMPLIFIED_READ_SUPPORTED

and PNG_SIMPLIFIED_WRITE_SUPPORTED undefined.

XVI. Other sources of information about libpng:

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.

Using the ./configure script -- 16 December 2002.

=================================================

The ./configure script should work compatibly with what scripts/makefile.*

did, however there are some options you might need to add to configure

explicitly, which previously was done semi-automatically (if you didn't edit

scripts/makefile.* yourself, that is)

CFLAGS="-Wall -O -funroll-loops \

-malign-loops=2 -malign-functions=2" ./configure --prefix=/usr/include \

--with-pkgconfigdir=/usr/lib/pkgconfig --includedir=/usr/include

You can alternatively specify --includedir=/usr/include, /usr/local/include,

/usr/include/libpng16, or whatever.

If you find that the configure script is out-of-date or is not supporting

your platform properly, try running autogen.sh to regenerate "configure",

"Makefile.in", and the other configuration files. Then try configure again.