1# scripts/pnglibconf.dfa - library build configuration control
  2#
  3@/*- pnglibconf.dfn intermediate file
  4@ *  generated from scripts/pnglibconf.dfa
  5@ */
  6#
  7com pnglibconf.h - library build configuration
  8com
  9version
 10com
 11com Copyright (c) 1998-2017 Glenn Randers-Pehrson
 12com
 13com This code is released under the libpng license.
 14com For conditions of distribution and use, see the disclaimer
 15com and license in png.h
 16com
 17
 18file pnglibconf.h scripts/pnglibconf.dfa PNGLCONF_H
 19
 20# This file is preprocessed by scripts/options.awk and the
 21# C compiler to generate 'pnglibconf.h' - a list of all the
 22# configuration options.  The file lists the various options
 23# that can *only* be specified during the libpng build;
 24# pnglibconf.h freezes the definitions selected for the specific
 25# build.
 26#
 27# The syntax is detailed in scripts/options.awk; this is a summary
 28# only:
 29#
 30# setting <name> [requires ...] [default]
 31#    #define PNG_<name> <value>  /* value comes from current setting */
 32# option <name> [requires ...] [if ...] [enables ...] [disabled]
 33#    #define PNG_<name>_SUPPORTED if the requirements are met and
 34#    enable the other options listed
 35# chunk <name> [requires ...] [enables ...] [disabled]
 36#    Enable chunk processing for the given ancillary chunk; any
 37#    'requires something' expands to READ_something for read and
 38#    WRITE_something for write, but the enables list members are
 39#    used as given (e.g. enables GAMMA just expands to that on the
 40#    correspond READ_name and WRITE_name lines.)
 41#
 42# "," may be used to separate options on an 'option' line and is ignored; it
 43# doesn't change the meaning of the line.  (NOT setting, where "," becomes
 44# part of the setting!)  A comma at the end of an option line causes a
 45# continuation (the next line is included in the option too.)
 46#
 47# Note that the 'on' and 'off' keywords, while valid on both option
 48# and chunk, should not be used in this file because they force the
 49# relevant options on or off.
 50
 51#----------------------------------------------------------------------
 52
 53# The following setting, option and chunk values can all be changed
 54# while building libpng:
 55#
 56# setting: change 'setting' lines to fine tune library performance;
 57#   changes to the settings don't affect the libpng API functionally
 58#
 59# option: change 'option' lines to remove or add capabilities from
 60#   or to the library; options change the library API
 61#
 62# chunk: change 'chunk' lines to remove capabilities to process
 63#   optional ('ancillary') chunks.  This does not prevent PNG
 64#   decoding but does change the libpng API because some chunks
 65#   will be ignored.
 66#
 67# There are three ways of disabling features, in no particular order:
 68#
 69# 1) Create 'pngusr.h', enter the required private build information
 70# detailed below and #define PNG_NO_<option> for each option you
 71# don't want in that file in that file.  You can also turn on options
 72# using PNG_<option>_SUPPORTED.  When you have finished rerun
 73# configure and rebuild pnglibconf.h file with -DPNG_USER_CONFIG:
 74#
 75#  make clean
 76#  CPPFLAGS='-DPNG_USER_CONFIG' ./configure
 77#  make pnglibconf.h
 78#
 79# pngusr.h is only used during the creation of pnglibconf.h, but it
 80# is safer to ensure that -DPNG_USER_CONFIG is specified throughout
 81# the build by changing the CPPFLAGS passed to the initial ./configure
 82#
 83# 2) Add definitions of the settings you want to change to
 84# CPPFLAGS; for example:
 85#
 86#   -DPNG_DEFAULT_READ_MACROS=0
 87#
 88# (This would change the default to *not* use read macros.)  Be
 89# very careful to change only settings that don't alter the API
 90# because this approach bypasses the private build checking.  You
 91# can also change settings from pngpriv.h (read pngpriv.h) safely
 92# without API changes.  Do that in the same way.
 93#
 94# 3) Write a new '.dfa' file (say 'pngusr.dfa') and in this file
 95# provide override values for setting entries and turn option or
 96# chunk values explicitly 'on' or 'off':
 97#
 98#    setting FOO default VALUE
 99#    option BAR [on|off]
100#
101# Then add this file to the options.awk command line (the *first*
102# one) after this file.  The make macro DFA_XTRA is provided to make
103# this easier (set it like CPPFLAGS prior to running ./configure).
104# Look at the builds below contrib/pngminim for some extreme examples
105# of how this can be used.
106#
107# Don't edit this file unless you are contributing a patch to
108# libpng and need new or modified options/settings.
109#----------------------------------------------------------------------
110
111# The following causes commented out #undef lines to be written to
112# pnglibconf.h; this can be stopped by logunsupported=0 in a later
113# file or on the command line (after pnglibconf.dfa)
114
115logunsupported = 1
116
117# The following allows the output from configure to modify the contents of
118# pnglibconf.h
119
120@#ifdef HAVE_CONFIG_H
121@#  include "config.h"
122@#endif
123
124# PNG_USER_CONFIG has to be defined on the compiler command line
125# to cause pngusr.h to be read while constructing pnglibconf.h
126#
127# If you create a private DLL you need to define the following
128# macros in the file 'pngusr.h' and set -DPNG_USER_CONFIG for
129# compilation (i.e. in CPPFLAGS.)
130# #define PNG_USER_PRIVATEBUILD \
131#     <Describes by whom and why this version of the DLL was built>
132#  e.g. #define PNG_USER_PRIVATEBUILD "Build by MyCompany for xyz reasons."
133# #define PNG_USER_DLLFNAME_POSTFIX <two-letter postfix that serve to
134#        distinguish your DLL from those of the official release. These
135#        correspond to the trailing letters that come after the version
136#        number and must match your private DLL name>
137#  e.g. // private DLL "libpng13gx.dll"
138#       #define PNG_USER_DLLFNAME_POSTFIX "gx"
139#
140# The following macros are also at your disposal if you want to complete the
141# DLL VERSIONINFO structure.
142# - PNG_USER_VERSIONINFO_COMMENTS
143# - PNG_USER_VERSIONINFO_COMPANYNAME
144# - PNG_USER_VERSIONINFO_LEGALTRADEMARKS
145
146# It is necessary to include configures definitions here so that AC_DEFINE
147# in configure.ac works in a comprehensible way
148@#if defined(HAVE_CONFIG_H) && !defined(PNG_NO_CONFIG_H)
149@#  include "config.h"
150@#endif
151
152@#ifdef PNG_USER_CONFIG
153@#  include "pngusr.h"
154@#endif
155
156# This is a special fixup for the Watcom C compiler on Windows, which has
157# multiple procedure call standards.  Unless PNG_API_RULE is set explicitly
158# (i.e. if it is not defined at this point) it will be forced to '2' here when
159# using Watcom.  This indicates to the other header files that Watcom behaviour
160# is required where appropriate.
161
162@#ifdef __WATCOMC__
163@#  ifndef PNG_API_RULE
164@#     define PNG_API_RULE 2 /* Use Watcom calling conventions */
165@#  endif
166@#endif
167
168# IN DEVELOPMENT
169# These are currently experimental features; define them if you want (NOTE:
170# experimental options must be disabled before they are defined in this file!)
171
172# NONE
173
174# Note that PNG_USER_CONFIG only has an effect when building
175# pnglibconf.h
176
177setting USER_CONFIG
178setting USER_PRIVATEBUILD
179setting USER_DLLFNAME_POSTFIX
180setting USER_VERSIONINFO_COMMENTS
181setting USER_VERSIONINFO_COMPANYNAME
182setting USER_VERSIONINFO_LEGALTRADEMARKS
183
184# Record the 'API rule' used to select calling conventions on
185# those systems that support such things (see all the comments in
186# pngconf.h)
187# Changing this setting has a fundamental affect on the PNG ABI,
188# do not release shared libraries with this changed.
189
190setting API_RULE default 0
191
192# This allows a prefix to be added to the front of every API functon name (and
193# therefore every symbol) by redefining all the function names with the prefix
194# at the end of pnglibconf.h.  It also turns on similar internal symbol renaming
195# by causing a similar build-time only file, pngprefix.h, to be generated.
196
197setting PREFIX
198
199# Implementation specific control of the optimizations, enabled by those
200# hardware or software options that need it (typically when run-time choices
201# must be made by the user)
202option SET_OPTION disabled
203
204# These options are specific to the ARM NEON hardware optimizations.  At present
205# these optimizations depend on GCC specific pre-processing of an assembler (.S)
206# file so they probably won't work with other compilers.
207#
208# ARM_NEON_OPT: unset: check at compile time (__ARM_NEON__ must be defined by
209#                      the compiler, typically as a result of specifying
210#                      CC="gcc -mfpu=neon".)
211#                   0: disable (even if the CPU has a NEON FPU.)
212#                   1: check at run time (via ARM_NEON_{API,CHECK})
213#                   2: switch on unconditionally (inadvisable - instead pass
214#                      -mfpu=neon to GCC in CC)
215#           When building libpng avoid using any setting other than '0'; '1' is
216#           set automatically when either 'API' or 'CHECK' are configured in,
217#           '2' should not be necessary as -mfpu=neon will achieve the same
218#           effect as well as applying NEON optimizations to the rest of the
219#           libpng code.
220#           NOTE: any setting other than '0' requires ALIGNED_MEMORY
221# ARM_NEON_API:   (PNG_ARM_NEON == 1) allow the optimization to be switched on
222#                 with png_set_option
223# ARM_NEON_CHECK: (PNG_ARM_NEON == 1) compile a run-time check to see if Neon
224#                 extensions are supported. This is poorly supported and
225#                 deprecated - use the png_set_option API.
226setting ARM_NEON_OPT
227option ARM_NEON_API disabled requires ALIGNED_MEMORY enables SET_OPTION,
228   sets ARM_NEON_OPT 1
229option ARM_NEON_CHECK disabled requires ALIGNED_MEMORY,
230   sets ARM_NEON_OPT 1
231
232# These options are specific to the PowerPC VSX hardware optimizations.
233#
234# POWERPC_VSX_OPT: unset: check at compile time (__PPC64__,__ALTIVEC__,__VSX__
235#                      must be defined by the compiler, typically as a result
236#                      of specifying
237#                      "-mvsx -maltivec" compiler flags)
238#                   0: disable (even if the CPU supports VSX.)
239#                   1: check at run time (via POWERPC_VSX_{API,CHECK})
240#                   2: switch on unconditionally (inadvisable - instead pass
241#                      -mvsx -maltivec to compiler options)
242#           When building libpng avoid using any setting other than '0'; '1' is
243#           set automatically when either 'API' or 'CHECK' are configured in,
244#           '2' should not be necessary as "-mvsx -maltivec" will achieve the same
245#           effect as well as applying VSX optimizations to the rest of the
246#           libpng code.
247# POWERPC_VSX_API:   (PNG_POWERPC_VSX == 1) allow the optimization to be switched on
248#                 with png_set_option
249# POWERPC_VSX_CHECK: (PNG_POWERPC_VSX == 1) compile a run-time check to see if VSX
250#                 extensions are supported. This is supported not for all OSes
251#                 (see contrib/powerpc/README)
252setting POWERPC_VSX_OPT
253option POWERPC_VSX_API disabled enables SET_OPTION,
254  sets POWERPC_VSX_OPT 1
255option POWERPC_VSX_CHECK disabled,
256  sets POWERPC_VSX_OPT 1
257
258
259# These settings configure the default compression level (0-9) and 'strategy';
260# strategy is as defined by the implementors of zlib. It describes the input
261# data and modifies the zlib parameters in an attempt to optimize the balance
262# between search and huffman encoding in the zlib algorithms.  The defaults are
263# the zlib.h defaults - the apparently recursive definition does not arise
264# because the name of the setting is prefixed by PNG_
265#
266# The TEXT values are the defaults when writing compressed text (all forms)
267
268# Include the zlib header so that the defaults below are known
269@#  include <zlib.h>
270
271# The '@' here means to substitute the value when pnglibconf.h is built
272setting Z_DEFAULT_COMPRESSION default @Z_DEFAULT_COMPRESSION
273# TODO: why aren't these Z_RLE; zlib.h says that Z_RLE, specifically, is
274# appropriate for PNG images, maybe it doesn't exist in all versions?
275setting Z_DEFAULT_STRATEGY default @Z_FILTERED
276setting Z_DEFAULT_NOFILTER_STRATEGY default @Z_DEFAULT_STRATEGY
277setting ZLIB_VERNUM default @ZLIB_VERNUM
278
279# Linkage of:
280#
281#  API:      libpng API functions
282#  CALLBACK: internal non-file-local callbacks
283#  FUNCTION: internal non-file-local functions
284#  DATA:     internal non-file-local (const) data
285setting LINKAGE_API default extern
286setting LINKAGE_CALLBACK default extern
287setting LINKAGE_FUNCTION default extern
288setting LINKAGE_DATA default extern
289
290setting TEXT_Z_DEFAULT_COMPRESSION default @Z_DEFAULT_COMPRESSION
291setting TEXT_Z_DEFAULT_STRATEGY default @Z_DEFAULT_STRATEGY
292
293# Default to using the read macros
294
295setting DEFAULT_READ_MACROS default 1
296
297# The alternative is to call functions to read PNG values, if
298# the functions are turned *off* the read macros must always
299# be enabled, so turning this off will actually force the
300# USE_READ_MACROS option on (see pngconf.h)
301
302option READ_INT_FUNCTIONS requires READ
303
304# The same for write  but these can only be switched off if no writing
305# is required at all - hence the use of a 'disabled', not a 'requires'.
306# If these are needed, they are enabled in the 'WRITE options' section
307# below.
308
309option WRITE_INT_FUNCTIONS disabled
310
311# Error controls
312#
313# WARNINGS: normally on, if off no warnings are generated
314# ERROR_TEXT: normally on, if off errors happen but there is no message
315# ERROR_NUMBERS: unimplemented feature, therefore disabled
316# BENIGN_ERRORS: support for just issuing warnings for recoverable errors
317#
318# BENIGN_READ_ERRORS:
319#     By default recoverable errors on read should just generate warnings,
320#     generally safe but PNG files that don't conform to the specification will
321#     be accepted if a meaningful result can be produced.
322#
323# BENIGN_WRITE_ERRORS:
324#     By default recoverable errors on write should just generate warnings,
325#     not generally safe because this allows the application to write invalid
326#     PNG files.  Applications should enable this themselves; it's useful
327#     because it means that a failure to write an ancilliary chunk can often be
328#     ignored.
329
330option WARNINGS
331option ERROR_TEXT
332option ERROR_NUMBERS disabled
333
334option BENIGN_ERRORS
335option BENIGN_WRITE_ERRORS requires BENIGN_ERRORS disabled
336option BENIGN_READ_ERRORS requires BENIGN_ERRORS
337
338
339# Generic options - affect both read and write.
340
341option MNG_FEATURES
342
343# Arithmetic options, the first is the big switch that chooses between internal
344# floating and fixed point arithmetic implementations - it does not affect any
345# APIs.  The second two (the _POINT settings) switch off individual APIs.
346#
347# Prior to libpng 1.6.8 one of the API (_POINT) variants had to be selected.  At
348# 1.6.8 this restriction has been removed; the simplified API can be used
349# without enabling any of the low level fixed/floating APIs.
350
351option FLOATING_ARITHMETIC
352option FLOATING_POINT
353option FIXED_POINT
354
355# This protects us against compilers that run on a windowing system
356# and thus don't have or would rather us not use the stdio types:
357# stdin, stdout, and stderr.  The only one currently used is stderr
358# in png_error() and png_warning().  #defining PNG_NO_CONSOLE_IO will
359# prevent these from being compiled and used. #defining PNG_NO_STDIO
360# will also prevent these, plus will prevent the entire set of stdio
361# macros and functions (FILE *, printf, etc.) from being compiled and used,
362# unless (PNG_DEBUG > 0) has been #defined.
363
364option STDIO
365option CONSOLE_IO requires STDIO
366
367# Note: prior to 1.5.0 this option could not be disabled if STDIO
368# was enabled.  Prior to 1.5.3 this option required STDIO
369
370option TIME_RFC1123
371
372# PNG_SETJMP_NOT_SUPPORTED is an old equivalent for NO_SETJMP
373
374option SETJMP
375= NO_SETJMP SETJMP_NOT_SUPPORTED
376
377# If this is disabled it is not possible for apps to get the
378# values from the 'info' structure, this effectively removes
379# quite a lot of the READ API.
380
381option EASY_ACCESS
382
383# Added at libpng-1.2.0
384
385option USER_MEM
386
387# Added at libpng-1.4.0
388
389option IO_STATE
390
391# Libpng limits: limit the size of images and data on read.
392#
393# If this option is disabled all the limit checking code will be disabled:
394
395option USER_LIMITS requires READ
396
397# The default settings given below for the limits mean that libpng will
398# limit the size of images or the size of data in ancilliary chunks to less
399# than the specification or implementation limits. Settings have the
400# following interpretations:
401#
402# USER_WIDTH_MAX: maximum width of an image that will be read
403# USER_HEIGHT_MAX: maximum height
404# USER_CHUNK_MALLOC_MAX: maximum in-memory (decompressed) size of a single chunk
405# USER_CHUNK_CACHE_MAX: maximum number of chunks to be cached
406#
407# Only chunks that are variable in number are counted towards the
408
409# Use 0x7fffffff for unlimited
410setting USER_WIDTH_MAX default        1000000
411setting USER_HEIGHT_MAX default       1000000
412
413# Use 0 for unlimited
414setting USER_CHUNK_CACHE_MAX default     1000
415setting USER_CHUNK_MALLOC_MAX default 8000000
416
417# If this option is enabled APIs to set the above limits at run time are added;
418# without this the hardwired (compile time) limits will be used.
419option SET_USER_LIMITS requires USER_LIMITS
420
421# All of the following options relate to code capabilities for
422# processing image data before creating a PNG or after reading one.
423# You can remove these capabilities safely and still be PNG
424# conformant, however the library that results is still non-standard.
425# See the comments above about how to change options and settings.
426
427# READ options
428#
429# WARNING: in libpng 1.5 maintained configuration compatibility with earlier
430# versions.  In some cases turning off an option turned off other options, in
431# others it was ineffective unless dependent options were also turned off.
432# Libpng 1.6 changes this: in general if you turn off an option that affects
433# APIs it stays off and simply disables APIs that depend on it.
434#
435# As a result if you simply port the libpng 1.5 configuration to libpng 1.6 you
436# will probably see build failures due to missing APIs.  Fixing these failures
437# requires some, perhaps considerable, knowledge of what your libpng using
438# applications are doing, fortunately there is no great reason for you to move
439# to libpng 1.6; the new interfaces in 1.6 will take several years to become
440# popular.
441
442option READ enables READ_INTERLACING SET_OPTION
443
444# Disabling READ_16BIT does not disable reading 16-bit PNG files, but it
445# forces them to be chopped down to 8-bit, and disables any 16-bit
446# processing after that has happened.  You need to be sure to enable
447# READ_SCALE_16_TO_8 or READ_STRIP_16_TO_8 when you disable READ_16BIT for
448# this to work properly.  You should disable the other option if you need to
449# ensure a particular conversion (otherwise the app can chose.)
450
451option READ_16BIT requires READ enables 16BIT
452
453option READ_QUANTIZE requires READ
454
455option READ_TRANSFORMS requires READ
456= NO_READ_TRANSFORMS READ_TRANSFORMS_NOT_SUPPORTED
457
458# Read gamma handling.  Gamma processing is a core part of libpng and many of
459# the capabilities are dependent on libpng performing gamma correction.
460#
461# In libpng 1.6 disabling gamma processing (setting PNG_NO_READ_GAMMA)
462# consistently disables those parts of the API that depend on it.  Prior to
463# 1.6.0 this was not true; the results were unpredictable and varied between
464# releases.
465#
466# If you disable gamma processing and your program no longer compiles you need
467# to ask whether you really need the APIs that are missing.  If you do then you
468# almost certainly need the gamma processing.
469#
470# If you handle gamma issues outside libpng then you do not need the libpng
471# gamma processing; and it is an enormous waste of space.  You just need to
472# remove the use of libpng APIs that depend on it.
473option READ_GAMMA requires READ_TRANSFORMS, READ_gAMA, READ_sRGB
474
475option READ_ALPHA_MODE requires READ_TRANSFORMS, READ_GAMMA
476option READ_BACKGROUND requires READ_TRANSFORMS, READ_STRIP_ALPHA, READ_GAMMA
477option READ_BGR requires READ_TRANSFORMS
478option READ_EXPAND_16 requires READ_TRANSFORMS, READ_16BIT, READ_EXPAND
479option READ_EXPAND requires READ_TRANSFORMS
480option READ_FILLER requires READ_TRANSFORMS
481option READ_GRAY_TO_RGB requires READ_TRANSFORMS
482option READ_INVERT_ALPHA requires READ_TRANSFORMS
483option READ_INVERT requires READ_TRANSFORMS
484option READ_PACK requires READ_TRANSFORMS
485option READ_PACKSWAP requires READ_TRANSFORMS
486option READ_RGB_TO_GRAY requires READ_TRANSFORMS, READ_GAMMA enables COLORSPACE
487option READ_SCALE_16_TO_8 requires READ_TRANSFORMS
488option READ_SHIFT requires READ_TRANSFORMS
489option READ_STRIP_16_TO_8 requires READ_TRANSFORMS
490option READ_STRIP_ALPHA requires READ_TRANSFORMS
491option READ_SWAP_ALPHA requires READ_TRANSFORMS
492option READ_SWAP requires READ_TRANSFORMS, READ_16BIT
493option READ_USER_TRANSFORM requires READ_TRANSFORMS
494
495option PROGRESSIVE_READ requires READ
496option SEQUENTIAL_READ requires READ
497
498# You can define PNG_NO_PROGRESSIVE_READ if you don't do progressive reading.
499# This is not talking about interlacing capability!  You'll still have
500# interlacing unless you turn off the following which is required
501# for PNG-compliant decoders.  (In other words, do not do this - in
502# fact it can't be disabled from the command line!)
503#option READ_INTERLACING requires READ
504
505option READ_COMPOSITE_NODIV requires READ
506= NO_READ_COMPOSITE_NODIV NO_READ_COMPOSITED_NODIV
507
508# Inch conversions
509
510option INCH_CONVERSIONS
511= INCH_CONVERSIONS INCH_CONVERSIONS
512
513# API to build a grayscale palette
514# NOTE: this is not used internally by libpng at present.
515
516option BUILD_GRAYSCALE_PALETTE
517
518# WRITE options
519
520option WRITE enables WRITE_INT_FUNCTIONS
521
522# Disabling WRITE_16BIT prevents 16-bit PNG files from being
523# generated.
524option WRITE_16BIT requires WRITE enables 16BIT
525
526option WRITE_TRANSFORMS requires WRITE
527= NO_WRITE_TRANSFORMS WRITE_TRANSFORMS_NOT_SUPPORTED
528
529option WRITE_SHIFT requires WRITE_TRANSFORMS
530option WRITE_PACK requires WRITE_TRANSFORMS
531option WRITE_BGR requires WRITE_TRANSFORMS
532option WRITE_SWAP requires WRITE_TRANSFORMS, WRITE_16BIT
533option WRITE_PACKSWAP requires WRITE_TRANSFORMS
534option WRITE_INVERT requires WRITE_TRANSFORMS
535option WRITE_FILLER requires WRITE_TRANSFORMS
536option WRITE_SWAP_ALPHA requires WRITE_TRANSFORMS
537option WRITE_INVERT_ALPHA requires WRITE_TRANSFORMS
538option WRITE_USER_TRANSFORM requires WRITE_TRANSFORMS
539
540# This is not required for PNG-compliant encoders, but can cause
541# trouble if left undefined
542
543option WRITE_INTERLACING requires WRITE
544
545# Deprecated, will be removed.
546option WRITE_WEIGHTED_FILTER requires WRITE
547
548option WRITE_FLUSH requires WRITE
549
550# Note: these can be turned off explicitly if not required by the
551# apps implementing the user transforms
552option USER_TRANSFORM_PTR if READ_USER_TRANSFORM, WRITE_USER_TRANSFORM
553option USER_TRANSFORM_INFO if READ_USER_TRANSFORM, WRITE_USER_TRANSFORM
554
555# This enables API to set compression parameters for compressing
556# non-IDAT chunks (zTXt, iTXt, iCCP, and unknown chunks).  This feature
557# was added at libpng-1.5.3.
558option WRITE_CUSTOMIZE_ZTXT_COMPRESSION requires WRITE
559option WRITE_CUSTOMIZE_COMPRESSION requires WRITE
560
561# Any chunks you are not interested in, you can undef here.  The
562# ones that allocate memory may be expecially important (hIST,
563# tEXt, zTXt, tRNS, pCAL).  Others will just save time and make png_info
564# a bit smaller.
565
566# The size of the png_text structure changed in libpng-1.0.6 when
567# iTXt support was added.  iTXt support was turned off by default through
568# libpng-1.2.x, to support old apps that malloc the png_text structure
569# instead of calling png_set_text() and letting libpng malloc it.  It
570# was turned on by default in libpng-1.4.0.
571
572option READ_ANCILLARY_CHUNKS requires READ
573# PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED is deprecated.
574= NO_READ_ANCILLARY_CHUNKS READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
575
576option WRITE_ANCILLARY_CHUNKS requires WRITE
577# PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED is deprecated.
578= NO_WRITE_ANCILLARY_CHUNKS WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
579
580# These options disable *all* the text chunks if turned off
581
582option TEXT disabled
583option READ_TEXT requires READ_ANCILLARY_CHUNKS enables TEXT
584option WRITE_TEXT requires WRITE_ANCILLARY_CHUNKS enables TEXT
585
586# Moved to pnglibconf.h at libpng-1.5.0
587# Feature support: in 1.4 this was in pngconf.h, but the following
588# features have no affect on the libpng API.  Add library
589# only features to the end of this list.  Add features that
590# affect the API above.  (Note: the list of chunks follows
591# the library-only settings.)
592#
593# BUILD TIME ONLY OPTIONS
594#   These options do not affect the API but rather alter how the
595#   API is implemented, they get recorded in pnglibconf.h, but
596#   can't be changed by the application.
597
598# Colorspace support (enabled as required); just the support for colorant
599# information.  Gamma support, likewise, is just support for the gamma
600# information, READ_GAMMA is required for gamma transformations (so it
601# is possible to read PNG gamma without enabling all the libpng transform
602# code - do this for applications that do their own gamma processing)
603#
604# As of 1.6.0 COLORSPACE is only useful if the application processes the
605# information; this is because the library does not do any colorspace
606# processing, it just validates the data in the PNG file.
607
608option GAMMA disabled
609option COLORSPACE enables GAMMA disabled
610
611# When an ICC profile is read, or png_set, it will be checked for a match
612# against known sRGB profiles if the sRGB handling is enabled.  The
613# PNG_sRGB_PROFILE_CHECKS setting controls how much work is done during the
614# check:
615#
616# -1: Don't do any sRGB profile checking.
617#
618#  0: Just validate the profile MD5 signature if present, otherwise use
619#     the checks in option 1.
620#
621#  1: Additionally check the length, intent and adler32 checksum of the
622#     actual data.   If enabled this will reject known profiles that have
623#     had the rendering intent in the header changed as well as other edits
624#     done without updating the checksum.  See the discussion below.
625#
626#  2: Additionally checksum all the data using the ethernet CRC32 algorithm.
627#     This makes it more difficult to fake profiles and makes it less likely
628#     to get a false positive on profiles with no signature, but is probably
629#     just a waste of time since all currently approved ICC sRGB profiles have
630#     a secure MD5 signature.
631#
632# The rendering intent.  An ICC profile stores an intended rendering intent,
633# but does not include the value in the signature.  The intent is documented
634# as the intent that should be used when combining two profiles.  The sRGB
635# profile is intended, however, to be used with any of the four defined intents.
636# For this reason the sRGB chunk includes an 'intent' to be used when displaying
637# the image (intent is really a property of the image not the profile.)
638#
639# Unfortunately the iCCP chunk does not.  It may therefore be that some
640# applications modify the intent in profiles (including sRGB profiles) to work
641# round this problem.  Selecting an option other than option '0' will cause such
642# modified profiles to be rejected.
643#
644# Security.  The use of Adler32 and CRC32 checksums does not help significantly
645# with any security issues.  It is relatively easy to produce arbitrary profiles
646# with the required checksums on current computer systems.  Nevertheless
647# security does not seem to be an issue because the only consequence of a false
648# positive is a false assertion that the profile is an sRGB profile.  This might
649# be used to hide data from libpng using applications, but it doesn't seem
650# possible to damage them.
651
652setting sRGB_PROFILE_CHECKS default 2
653
654# Artificially align memory - the code typically aligns to 8 byte
655# boundaries if this is switched on, it's a small waste of space
656# but can help (in theory) on some architectures.  Only affects
657# internal structures.  Added at libpng 1.4.0
658
659option ALIGNED_MEMORY
660
661# Buggy compilers (e.g., gcc 2.7.2.2) need PNG_NO_POINTER_INDEXING
662# See png[wr]util.c, normally this should always be *on*
663
664option POINTER_INDEXING
665
666# Other defines for things like memory and the like can go here.
667
668# BUILD TIME SETTINGS
669# Like build time options these do not affect the API, but they
670# may be useful to applications because they record details of
671# how the API will behave particularly with regard to overall
672# accuracy.
673
674# This controls how fine the quantizing gets.  As this allocates
675# a largish chunk of memory (32K), those who are not as concerned
676# with quantizing quality can decrease some or all of these.
677
678setting QUANTIZE_RED_BITS default 5
679setting QUANTIZE_GREEN_BITS default 5
680setting QUANTIZE_BLUE_BITS default 5
681
682# This controls how fine the gamma correction becomes when you
683# are only interested in 8 bits anyway.  Increasing this value
684# results in more memory being used, and more pow() functions
685# being called to fill in the gamma tables.  Don't set this value
686# less than 8, and even that may not work (I haven't tested it).
687
688setting MAX_GAMMA_8 default 11
689
690# This controls how much a difference in gamma we can tolerate before
691# we actually start doing gamma conversion, it's a fixed point value,
692# so the default below is 0.05, meaning libpng ignores corrections in
693# the range 0.95 to 1.05
694
695setting GAMMA_THRESHOLD_FIXED default 5000
696
697# Precision to use when converting a floating point value to a PNG
698# extension format string in an sCAL chunk (only relevant if the
699# floating point API is enabled)
700
701setting sCAL_PRECISION default 5
702
703# This is the size of the compression buffer, and thus the size of
704# an IDAT chunk.  Make this whatever size you feel is best for your
705# machine.  One of these will be allocated per png_struct.  When this
706# is full, it writes the data to the disk, and does some other
707# calculations.  Making this an extremely small size may slow
708# the library down, but you may want to experiment to determine
709# where it becomes significant, if you are concerned with memory
710# usage.  Note that zlib allocates at least 32Kb also.  For readers,
711# this describes the size of the buffer available to read the data in.
712# Unless this gets smaller than the size of a row (compressed),
713# it should not make much difference how big this is.
714
715setting ZBUF_SIZE default 8192
716
717# This is the size of the decompression buffer used when counting or checking
718# the decompressed size of an LZ stream from a compressed ancilliary chunk; the
719# decompressed data is never used so a different size may be optimal.  This size
720# was determined using contrib/libtests/timepng.c with compressed zTXt data
721# around 11MByte in size.  Slight speed improvements (up to about 14% in
722# timepng) can be achieved by very large increases (to 32kbyte) on regular data,
723# but highly compressible data shows only around 2% improvement.   The size is
724# chosen to minimize the effects of DoS attacks based on using very large
725# amounts of highly compressible data.
726
727setting INFLATE_BUF_SIZE default 1024
728
729# This is the maximum amount of IDAT data that the sequential reader will
730# process at one time.  The setting does not affect the size of IDAT chunks
731# read, just the amount read at once.  Neither does it affect the progressive
732# reader, which processes just the amount of data the application gives it.
733# The sequential reader is currently unable to process more than one IDAT at
734# once - it has to read and process each one in turn.  There is no point setting
735# this to a value larger than the IDAT chunks typically encountered (it would
736# just waste memory) but there may be some point in reducing it below the value
737# of ZBUF_SIZE (the size of IDAT chunks written by libpng.)
738
739setting IDAT_READ_SIZE default PNG_ZBUF_SIZE
740
741# Ancillary chunks
742chunk bKGD
743chunk cHRM enables COLORSPACE
744chunk eXIf
745chunk gAMA enables GAMMA
746chunk hIST
747chunk iCCP enables COLORSPACE, GAMMA
748chunk iTXt enables TEXT
749chunk oFFs
750chunk pCAL
751chunk pHYs
752chunk sBIT
753chunk sCAL
754chunk sPLT
755chunk sRGB enables COLORSPACE, GAMMA, SET_OPTION
756chunk tEXt requires TEXT
757chunk tIME
758chunk tRNS
759chunk zTXt enables TEXT
760
761# This only affects support of the optional PLTE chunk in RGB and RGBA
762# images.  Notice that READ_ANCILLARY_CHUNKS therefore disables part
763# of the regular chunk reading too.
764
765option READ_OPT_PLTE requires READ_ANCILLARY_CHUNKS
766
767# Unknown chunk handling
768#
769# 'UNKNOWN_CHUNKS' is a global option to disable all unknown chunk handling on
770# read or write; everything else below requires it (directly or indirectly).
771option UNKNOWN_CHUNKS
772
773# There are three main options to control the ability to read and write unknown
774# chunks.  If either read option is turned on then unknown chunks will be read,
775# otherwise they are skipped.  If the write option is turned on unknown chunks
776# set by png_set_unknown_chunks will be written otherwise it is an error to call
777# that API on a write struct.
778option WRITE_UNKNOWN_CHUNKS requires WRITE requires UNKNOWN_CHUNKS
779option WRITE_UNKNOWN_CHUNKS enables STORE_UNKNOWN_CHUNKS
780
781# The first way to read user chunks is to have libpng save them for a later call
782# to png_get_unknown_chunks, the application must call
783# png_set_keep_unknown_chunks to cause this to actually happen (see png.h)
784option SAVE_UNKNOWN_CHUNKS requires READ requires SET_UNKNOWN_CHUNKS
785option SAVE_UNKNOWN_CHUNKS enables READ_UNKNOWN_CHUNKS, STORE_UNKNOWN_CHUNKS
786
787# The second approach is to use an application provided callback to process the
788# chunks, the callback can either handle the chunk entirely itself or request
789# that libpng store the chunk for later retrieval via png_get_unknown_chunks.
790#
791# NOTE: If STORE_UNKNOWN_CHUNKS is not enabled (which is the default if
792# both SAVE_UNKNOWN_CHUNKS and WRITE_UNKNOWN_CHUNKS are disabled) then a
793# 0 result from the callback will be ignored because no support for saving
794# unknown chunks has been compiled in.  The normal symptom is that your app
795# fails to compile because png_get_unknown_chunks is no longer defined in png.h.
796# If you encounter this issue simply enable STORE_UNKNOWN_CHUNKS in your build.
797#
798# Note that there is no 'WRITE_USER_CHUNKS' so the USER_CHUNKS option is always
799# the same as READ_USER_CHUNKS at present
800option READ_USER_CHUNKS requires READ, UNKNOWN_CHUNKS
801option READ_USER_CHUNKS enables READ_UNKNOWN_CHUNKS, USER_CHUNKS
802
803# Two further options are provided to allow detailed control of the handling.
804# The first enables png_set_keep_unknown_chunks; this allows the default to be
805# changed from discarding unknown chunks and allows per-chunk control.  This is
806# required to use the SAVE_UNKNOWN_CHUNKS option.  If enabled this option also
807# applies to write (see png.h), otherwise the write API simply writes all the
808# chunks it is given.
809#
810# The second option extends the unknown handling to allow known chunks to be
811# handled as though they were unknown.  This option doesn't change any APIs, it
812# merely turns on the code to check known as well as unknown chunks.
813#
814# This option no longer affects the write code.  It can be safely disabled and
815# will prevent applications stopping libpng reading known chunks.
816option SET_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS
817option HANDLE_AS_UNKNOWN requires SET_UNKNOWN_CHUNKS
818
819# The following options are derived from the above and should not be turned on
820# explicitly.
821option READ_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
822option STORE_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
823
824option CONVERT_tIME requires WRITE_ANCILLARY_CHUNKS
825# The "tm" structure is not supported on WindowsCE
826
827@#ifdef _WIN32_WCE
828@#   define PNG_NO_CONVERT_tIME
829@#endif
830
831option WRITE_FILTER requires WRITE
832
833option SAVE_INT_32 disabled
834# png_save_int_32 is required internally for writing the ancillary chunks oFFs
835# and pCAL and for both reading and writing iCCP (for the generation/checking of
836# the corresponding cHRM/gAMA chunks) if full ICC is supported.
837
838# added at libpng-1.5.4
839
840option WRITE_OPTIMIZE_CMF requires WRITE
841
842option READ_COMPRESSED_TEXT disabled
843option READ_iCCP enables READ_COMPRESSED_TEXT
844option READ_iTXt enables READ_COMPRESSED_TEXT
845option READ_zTXt enables READ_COMPRESSED_TEXT
846
847option WRITE_oFFs enables SAVE_INT_32
848option WRITE_pCAL enables SAVE_INT_32
849option WRITE_cHRM enables SAVE_INT_32
850
851option WRITE_COMPRESSED_TEXT disabled
852option WRITE_iCCP enables WRITE_COMPRESSED_TEXT
853option WRITE_iTXt enables WRITE_COMPRESSED_TEXT
854option WRITE_zTXt enables WRITE_COMPRESSED_TEXT
855
856# Turn this off to disable png_read_png() and png_write_png() and
857# leave the row_pointers member out of the info structure.
858
859option INFO_IMAGE
860
861# added at libpng-1.5.10
862# Turn this off to disable warning about invalid palette index and
863# leave the num_palette_max member out of the png structure.
864
865option CHECK_FOR_INVALID_INDEX enables READ_CHECK_FOR_INVALID_INDEX
866option CHECK_FOR_INVALID_INDEX enables WRITE_CHECK_FOR_INVALID_INDEX
867option READ_CHECK_FOR_INVALID_INDEX requires READ, CHECK_FOR_INVALID_INDEX
868option WRITE_CHECK_FOR_INVALID_INDEX requires WRITE, CHECK_FOR_INVALID_INDEX
869
870# added at libpng-1.5.15
871option GET_PALETTE_MAX enables READ_GET_PALETTE_MAX WRITE_GET_PALETTE_MAX
872option READ_GET_PALETTE_MAX requires READ_CHECK_FOR_INVALID_INDEX disabled
873option WRITE_GET_PALETTE_MAX requires WRITE_CHECK_FOR_INVALID_INDEX disabled
874
875# Simplified API options (added at libpng-1.6.0)
876#  In libpng 1.6.8 the handling of these options was changed to used 'requires'
877#  throughout, so that disabling some of the low level support always disables
878#  the base simplified read/write API.  This much simplifies the handling and
879#  makes 'everything = off' work in a more intuitive way.  It eliminates a
880#  previously reported feature that APIs previously enabled by the simplified
881#  API couldn't be turned off without explicitly turning off the simplified
882#  APIs.
883#
884# Read:
885option SIMPLIFIED_READ,
886   requires SEQUENTIAL_READ, READ_TRANSFORMS, SETJMP, BENIGN_ERRORS,
887      READ_EXPAND, READ_16BIT, READ_EXPAND_16, READ_SCALE_16_TO_8,
888      READ_RGB_TO_GRAY, READ_ALPHA_MODE, READ_BACKGROUND, READ_STRIP_ALPHA,
889      READ_FILLER, READ_SWAP, READ_PACK, READ_GRAY_TO_RGB, READ_GAMMA,
890      READ_tRNS, READ_bKGD, READ_gAMA, READ_cHRM, READ_sRGB, READ_sBIT
891
892# AFIRST and BGR read options:
893#  Prior to libpng 1.6.8 these were disabled but switched on if the low level
894#  libpng routines that do the swaps were enabled.  This worked but was
895#  confusing.  In libpng 1.6.8 the options were changed to simple 'requires'
896#  and are enabled by default.  This should work the same way in practice.
897option SIMPLIFIED_READ_AFIRST enables FORMAT_AFIRST,
898   requires SIMPLIFIED_READ READ_SWAP_ALPHA
899
900option SIMPLIFIED_READ_BGR enables FORMAT_BGR,
901   requires SIMPLIFIED_READ READ_BGR
902
903# Write:
904option SIMPLIFIED_WRITE,
905   requires WRITE, SETJMP, WRITE_SWAP, WRITE_PACK,
906      WRITE_tRNS, WRITE_gAMA, WRITE_sRGB, WRITE_cHRM
907
908# 1.6.22: allow simplified write without stdio support:
909option SIMPLIFIED_WRITE_STDIO requires SIMPLIFIED_WRITE STDIO
910
911option SIMPLIFIED_WRITE_AFIRST enables FORMAT_AFIRST,
912   requires SIMPLIFIED_WRITE WRITE_SWAP_ALPHA
913
914option SIMPLIFIED_WRITE_BGR enables FORMAT_BGR,
915   requires SIMPLIFIED_WRITE WRITE_BGR
916
917# Formats:
918option FORMAT_AFIRST disabled
919option FORMAT_BGR disabled