[libpng16] Moved part of INSTALL back to manual; added table of contents.
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Glenn Randers-Pehrson
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293
INSTALL
293
INSTALL
@ -41,33 +41,19 @@ is not already on your system. zlib can usually be found
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wherever you got libpng. zlib can be placed in another directory,
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at the same level as libpng.
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If your system already has a preinstalled zlib you will still need
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to have access to the zlib.h and zconf.h include files that
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correspond to the version of zlib that's installed.
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If you wish to test with a particular zlib that is not first in the
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standard library search path, put ZLIBLIB, ZLIBINC, CPPFLAGS, LDFLAGS,
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and LD_LIBRARY_PATH in your environment before running "make test"
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or "make distcheck":
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ZLIBLIB=/path/to/lib export ZLIBLIB
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ZLIBINC=/path/to/include export ZLIBINC
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CPPFLAGS="-I$ZLIBINC" export CPPFLAGS
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LDFLAGS="-L$ZLIBLIB" export LDFLAGS
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LD_LIBRARY_PATH="$ZLIBLIB:$LD_LIBRARY_PATH" export LD_LIBRARY_PATH
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If you are using one of the makefile scripts, put ZLIBLIB and ZLIBINC
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in your environment and type "make ZLIBLIB=$ZLIBLIB ZLIBINC=$ZLIBINC test".
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If you want to use "cmake" (see www.cmake.org), type
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cmake . -DCMAKE_INSTALL_PREFIX=/path
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make
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make install
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If your system already has a preinstalled zlib you will still need
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to have access to the zlib.h and zconf.h include files that
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correspond to the version of zlib that's installed.
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You can rename the directories that you downloaded (they
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might be called "libpng-x.y.z" or "libpngNN" and "zlib-1.2.7"
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or "zlib127") so that you have directories called "zlib" and "libpng".
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might be called "libpng-x.y.z" or "libpngNN" and "zlib-1.2.5"
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or "zlib125") so that you have directories called "zlib" and "libpng".
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Your directory structure should look like this:
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@ -85,7 +71,6 @@ Your directory structure should look like this:
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depcomp, install-sh, mkinstalldirs, test-pngtest.sh
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contrib
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gregbook
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libtests
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pngminim
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pngminus
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pngsuite
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@ -145,272 +130,6 @@ do that, run "make install" in the zlib directory first if necessary).
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Some also allow you to run "make test-installed" after you have
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run "make install".
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Configuring libpng for 16-bit platforms
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You will want to look into zconf.h to tell zlib (and thus libpng) that
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it cannot allocate more then 64K at a time. Even if you can, the memory
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won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
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Configuring for DOS
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For DOS users who only have access to the lower 640K, you will
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have to limit zlib's memory usage via a png_set_compression_mem_level()
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call. See zlib.h or zconf.h in the zlib library for more information.
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Configuring for Medium Model
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Libpng's support for medium model has been tested on most of the popular
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compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
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defined, and FAR gets defined to far in pngconf.h, and you should be
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all set. Everything in the library (except for zlib's structure) is
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expecting far data. You must use the typedefs with the p or pp on
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the end for pointers (or at least look at them and be careful). Make
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note that the rows of data are defined as png_bytepp, which is
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an "unsigned char far * far *".
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Prepending a prefix to exported symbols
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Starting with libpng-1.6.0, you can configure libpng (when using the
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"configure" script) to prefix all exported symbols by means of the
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configuration option "--with-libpng-prefix=FOO_", where FOO_ can be any
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string beginning with a letter and containing only uppercase
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and lowercase letters, digits, and the underscore (i.e., a C language
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identifier). This creates a set of macros in pnglibconf.h, so this is
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transparent to applications; their function calls get transformed by
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the macros to use the modified names.
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Configuring for compiler xxx:
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All includes for libpng are in pngconf.h. If you need to add, change
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or delete an include, this is the place to do it.
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The includes that are not needed outside libpng are placed in pngpriv.h,
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which is only used by the routines inside libpng itself.
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The files in libpng proper only include pngpriv.h and png.h, which
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in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
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As of libpng-1.5.0, pngpriv.h also includes three other private header
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files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
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that previously appeared in the public headers.
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Removing unwanted object code
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There are a bunch of #define's in pngconf.h that control what parts of
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libpng are compiled. All the defines end in _SUPPORTED. If you are
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never going to use a capability, you can change the #define to #undef
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before recompiling libpng and save yourself code and data space, or
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you can turn off individual capabilities with defines that begin with
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PNG_NO_.
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In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead.
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You can also turn all of the transforms and ancillary chunk capabilities
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off en masse with compiler directives that define
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PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
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or all four, along with directives to turn on any of the capabilities that
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you do want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the
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extra transformations but still leave the library fully capable of reading
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and writing PNG files with all known public chunks. Use of the
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PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library
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that is incapable of reading or writing ancillary chunks. If you are
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not using the progressive reading capability, you can turn that off
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with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING
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capability, which you'll still have).
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All the reading and writing specific code are in separate files, so the
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linker should only grab the files it needs. However, if you want to
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make sure, or if you are building a stand alone library, all the
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reading files start with "pngr" and all the writing files start with "pngw".
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The files that don't match either (like png.c, pngtrans.c, etc.)
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are used for both reading and writing, and always need to be included.
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The progressive reader is in pngpread.c
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If you are creating or distributing a dynamically linked library (a .so
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or DLL file), you should not remove or disable any parts of the library,
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as this will cause applications linked with different versions of the
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library to fail if they call functions not available in your library.
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The size of the library itself should not be an issue, because only
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those sections that are actually used will be loaded into memory.
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Changes to the build and configuration of libpng in libpng-1.5.x
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Details of internal changes to the library code can be found in the CHANGES
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file and in the GIT repository logs. These will be of no concern to the vast
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majority of library users or builders; however, the few who configure libpng
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to a non-default feature set may need to change how this is done.
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There should be no need for library builders to alter build scripts if
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these use the distributed build support - configure or the makefiles -
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however, users of the makefiles may care to update their build scripts
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to build pnglibconf.h where the corresponding makefile does not do so.
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Building libpng with a non-default configuration has changed completely.
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The old method using pngusr.h should still work correctly even though the
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way pngusr.h is used in the build has been changed; however, library
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builders will probably want to examine the changes to take advantage of
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new capabilities and to simplify their build system.
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1. Specific changes to library configuration capabilities
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The library now supports a complete fixed point implementation and can
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thus be used on systems that have no floating point support or very
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limited or slow support. Previously gamma correction, an essential part
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of complete PNG support, required reasonably fast floating point.
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As part of this the choice of internal implementation has been made
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independent of the choice of fixed versus floating point APIs and all the
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missing fixed point APIs have been implemented.
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The exact mechanism used to control attributes of API functions has
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changed. A single set of operating system independent macro definitions
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is used and operating system specific directives are defined in
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pnglibconf.h
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As part of this the mechanism used to choose procedure call standards on
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those systems that allow a choice has been changed. At present this only
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affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
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running on Intel processors. As before, PNGAPI is defined where required
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to control the exported API functions; however, two new macros, PNGCBAPI
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and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
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(PNGCAPI) for functions that must match a C library prototype (currently
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only png_longjmp_ptr, which must match the C longjmp function.) The new
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approach is documented in pngconf.h
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Despite these changes, libpng 1.5.0 only supports the native C function
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calling standard on those platforms tested so far (__cdecl on Microsoft
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Windows). This is because the support requirements for alternative
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calling conventions seem to no longer exist. Developers who find it
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necessary to set PNG_API_RULE to 1 should advise the mailing list
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(png-mng-implement) of this and library builders who use Openwatcom and
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therefore set PNG_API_RULE to 2 should also contact the mailing list.
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A new test program, pngvalid, is provided in addition to pngtest.
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pngvalid validates the arithmetic accuracy of the gamma correction
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calculations and includes a number of validations of the file format.
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A subset of the full range of tests is run when "make check" is done
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(in the 'configure' build.) pngvalid also allows total allocated memory
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usage to be evaluated and performs additional memory overwrite validation.
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Many changes to individual feature macros have been made. The following
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are the changes most likely to be noticed by library builders who
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configure libpng:
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1) All feature macros now have consistent naming:
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#define PNG_NO_feature turns the feature off
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#define PNG_feature_SUPPORTED turns the feature on
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pnglibconf.h contains one line for each feature macro which is either:
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#define PNG_feature_SUPPORTED
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if the feature is supported or:
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/*#undef PNG_feature_SUPPORTED*/
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if it is not. Library code consistently checks for the 'SUPPORTED' macro.
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It does not, and libpng applications should not, check for the 'NO' macro
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which will not normally be defined even if the feature is not supported.
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The 'NO' macros are only used internally for setting or not setting the
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corresponding 'SUPPORTED' macros.
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Compatibility with the old names is provided as follows:
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PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED
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And the following definitions disable the corresponding feature:
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PNG_SETJMP_NOT_SUPPORTED disables SETJMP
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PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS
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PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV
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PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS
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PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS
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PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS
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Library builders should remove use of the above, inconsistent, names.
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2) Warning and error message formatting was previously conditional on
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the STDIO feature. The library has been changed to use the
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CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled
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the library no longer uses the printf(3) functions, even though the
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default read/write implementations use (FILE) style stdio.h functions.
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3) Three feature macros now control the fixed/floating point decisions:
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PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs
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PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in
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practice these are normally required internally anyway (because the PNG
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file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT
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merely stops the function from being exported.
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PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating
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point implementation or the fixed point one. Typically the fixed point
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implementation is larger and slower than the floating point implementation
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on a system that supports floating point; however, it may be faster on a
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system which lacks floating point hardware and therefore uses a software
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emulation.
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4) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the
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functions to read and write ints to be disabled independently of
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PNG_USE_READ_MACROS, which allows libpng to be built with the functions
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even though the default is to use the macros - this allows applications
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to choose at app buildtime whether or not to use macros (previously
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impossible because the functions weren't in the default build.)
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2. Changes to the configuration mechanism
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Prior to libpng-1.5.0 library builders who needed to configure libpng
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had either to modify the exported pngconf.h header file to add system
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specific configuration or had to write feature selection macros into
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pngusr.h and cause this to be included into pngconf.h by defining
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PNG_USER_CONFIG. The latter mechanism had the disadvantage that an
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application built without PNG_USER_CONFIG defined would see the
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unmodified, default, libpng API and thus would probably fail to link.
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These mechanisms still work in the configure build and in any makefile
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build that builds pnglibconf.h, although the feature selection macros
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have changed somewhat as described above. In 1.5.0, however, pngusr.h is
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processed only once, when the exported header file pnglibconf.h is built.
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pngconf.h no longer includes pngusr.h, therefore pngusr.h is ignored after the
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build of pnglibconf.h and it is never included in an application build.
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The rarely used alternative of adding a list of feature macros to the
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CPPFLAGS setting in the build also still works; however, the macros will be
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copied to pnglibconf.h and this may produce macro redefinition warnings
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when the individual C files are compiled.
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All configuration now only works if pnglibconf.h is built from
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scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan
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(the original author of awk) maintains C source code of that awk and this
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and all known later implementations (often called by subtly different
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names - nawk and gawk for example) are adequate to build pnglibconf.h.
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The Sun Microsystems (now Oracle) program 'awk' is an earlier version
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and does not work; this may also apply to other systems that have a
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functioning awk called 'nawk'.
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Configuration options are now documented in scripts/pnglibconf.dfa. This
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file also includes dependency information that ensures a configuration is
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consistent; that is, if a feature is switched off dependent features are
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also removed. As a recommended alternative to using feature macros in
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pngusr.h a system builder may also define equivalent options in pngusr.dfa
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(or, indeed, any file) and add that to the configuration by setting
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DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate
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how to do this, and a case where pngusr.h is still required.
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Configuring libpng for multiprocessing
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Libpng uses setjmp()/longjmp() for error handling. Unfortunately setjmp()
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is known to be not thread-safe on some platforms and we don't know of
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any platform where it is guaranteed to be thread-safe. Therefore, if
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your application is going to be using multiple threads, you should
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configure libpng with PNG_NO_SETJMP in your pngusr.dfa file, with
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-DPNG_NO_SETJMP on your compile line, or with
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#undef PNG_SETJMP_SUPPORTED
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in your pnglibconf.h or pngusr.h.
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Other sources of information about libpng:
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Further information can be found in the README and libpng-manual.txt
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files, in the individual makefiles, in png.h, and the manual pages
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libpng.3 and png.5.
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