[devel] Minor editing of the manual.
diff --git a/libpng-manual.txt b/libpng-manual.txt
index 15a3c1a..a1a6db7 100644
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -1,6 +1,6 @@
libpng-manual.txt - A description on how to use and modify libpng
- libpng version 1.5.5beta01 - July 10, 2011
+ libpng version 1.5.5beta01 - July 12, 2011
Updated and distributed by Glenn Randers-Pehrson
<glennrp at users.sourceforge.net>
Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -11,7 +11,7 @@
Based on:
- libpng versions 0.97, January 1998, through 1.5.5beta01 - July 10, 2011
+ libpng versions 0.97, January 1998, through 1.5.5beta01 - July 12, 2011
Updated and distributed by Glenn Randers-Pehrson
Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -116,14 +116,23 @@
Many (in particular the png_set and png_get APIs) also require a pointer
to png_info as the second argument. Some application visible macros
defined in png.h designed for basic data access (reading and writing
-integers in the PNG format) break this rule, but it's almost always safe
-to assume that a (png_struct*) has to be passed to call an API function.
+integers in the PNG format) don't take a png_info pointer, but it's almost
+always safe to assume that a (png_struct*) has to be passed to call an API
+function.
+
+You can have more than one png_info structure associated with an image,
+as illustrated in pngtest.c, one for information valid prior to the
+IDAT chunks and another (called "end_info" below) for things after them.
The png.h header file is an invaluable reference for programming with libpng.
And while I'm on the topic, make sure you include the libpng header file:
#include <png.h>
+and also (as of libpng-1.5.0) the zlib header file, if you need it:
+
+#include <zlib.h>
+
Types
The png.h header file defines a number of integral types used by the
@@ -165,7 +174,7 @@
of libpng are recorded in the header file "pnglibconf.h" and this file
is always included by png.h.
-If you don't need to change the library configuration from the default skip to
+If you don't need to change the library configuration from the default, skip to
the next section ("Reading").
Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
@@ -238,6 +247,10 @@
but most of them have no visible effect on the API. Some can also be overridden
from the API.
+This method of building a customized pnglibconf.h is illustrated in
+contrib/pngminim/*. See the "$(PNGCONF):" target in the makefile and
+pngusr.dfa in these directories.
+
C. Configuration using PNG_USR_CONFIG
If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
@@ -274,6 +287,9 @@
dependency information for each setting and option. Simply locate the
feature in the file and read the C comments that precede it.
+This method is also illustrated in the contrib/pngminim/* makefiles and
+pngusr.h.
+
III. Reading
We'll now walk you through the possible functions to call when reading
@@ -3448,7 +3464,8 @@
after a longjmp, so the user may want to be careful about doing anything
after setjmp returns non-zero besides returning itself. Consult your
compiler documentation for more details. For an alternative approach, you
-may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net).
+may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
+which is illustrated in pngvalid.c and in contrib/visupng.
Custom chunks
@@ -3466,8 +3483,11 @@
similarly. Second, check out the sections of libpng that read and
write chunks. Try to find a chunk that is similar to yours and use
it as a template. More details can be found in the comments inside
-the code. It is best to handle unknown chunks in a generic method,
-via callback functions, instead of by modifying libpng functions.
+the code. It is best to handle private or unknown chunks in a generic method,
+via callback functions, instead of by modifying libpng functions. This
+is illustrated in pngtest.c, which uses a callback function to handle a
+private "vpAg" chunk and the new "sTER" chunk, which are both unknown to
+libpng.
If you wish to write your own transformation for the data, look through
the part of the code that does the transformations, and check out some of
@@ -3663,8 +3683,8 @@
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.)
+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
@@ -4042,7 +4062,6 @@
libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls
the application-provided png_longjmp_ptr on the internal, but application
-initialized, jmpbuf. It is provided as a convenience to avoid the need
initialized, longjmp buffer. It is provided as a convenience to avoid
the need to use the png_jmpbuf macro, which had the unnecessary side
effect of resetting the internal png_longjmp_ptr value.
@@ -4121,9 +4140,9 @@
B. Changes to the build and configuration of libpng
Details of internal changes to the library code can be found in the CHANGES
-file. 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.
+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 -
@@ -4132,14 +4151,14 @@
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
+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.
B.1 Specific changes to library configuration capabilities
The library now supports a complete fixed point implementation and can
-thus be used on systems which have no floating point support or very
+thus be used on systems that have no floating point support or very
limited or slow support. Previously gamma correction, an essential part
of complete PNG support, required reasonably fast floating point.
@@ -4155,14 +4174,14 @@
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
+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
+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
@@ -4196,7 +4215,9 @@
if it is not. Library code consistently checks for the 'SUPPORTED' macro.
It does not, and should not, check for the 'NO' macro which will not
-normally be defined even if the feature is not supported.
+normally be defined even if the feature is not supported. The 'NO' macros
+are only used internally for setting the corresponding 'SUPPORTED' macros
+or not.
Compatibility with the old names is provided as follows:
@@ -4253,10 +4274,10 @@
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
+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, when the exported header file pnglibconf.h is built.
-pngconf.h no longer includes pngusr.h, therefore it is ignored after the
+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 rarely used alternative of adding a list of feature macros to the
@@ -4270,7 +4291,7 @@
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
+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
@@ -4312,8 +4333,8 @@
We also accept patches built from the tar or zip distributions, and
simple verbal discriptions of bug fixes, reported either to the
-SourceForge bug tracker or to the png-mng-implement at lists.sf.net
-mailing list.
+SourceForge bug tracker, to the png-mng-implement at lists.sf.net
+mailing list, or directly to glennrp.
XIII. Coding style
@@ -4426,7 +4447,7 @@
XIV. Y2K Compliance in libpng
-July 10, 2011
+July 12, 2011
Since the PNG Development group is an ad-hoc body, we can't make
an official declaration.