com
version
com
-com Copyright (c) 1998-2011 Glenn Randers-Pehrson
+com Copyright (c) 1998-2012 Glenn Randers-Pehrson
com
com This code is released under the libpng license.
com For conditions of distribution and use, see the disclaimer
# pnglibconf.h freezes the definitions selected for the specific
# build.
#
-# The syntax is detailed in scripts/options.awk, this is a summary
+# The syntax is detailed in scripts/options.awk; this is a summary
# only:
#
# setting <name> [default]
# option <name> [requires ...] [if ...] [enables ...] [disabled]
# #define PNG_<name>_SUPPORTED if the requirements are met and
# enable the other options listed
-# chunk <name> [requires ...] [disabled]
-# Enable chunk processing for the given ancillary chunk
+# chunk <name> [requires ...] [enables ...] [disabled]
+# Enable chunk processing for the given ancillary chunk; any
+# 'requires something' expands to READ_something for read and
+# WRITE_something for write, but the enables list members are
+# used as given (e.g. enables GAMMA just expands to that on the
+# correspond READ_name and WRITE_name lines.)
#
# Note that the 'on' and 'off' keywords, while valid on both option
# and chunk, should not be used in this file because they force the
# The following setting, option and chunk values can all be changed
# while building libpng:
#
-# setting: change 'setting' lines to fine tune library performance,
+# setting: change 'setting' lines to fine tune library performance;
# changes to the settings don't affect the libpng API functionally
#
# option: change 'option' lines to remove or add capabilities from
@# endif
@#endif
+# IN DEVELOPMENT
+# These are currently experimental features; define them if you want (NOTE:
+# experimental options must be disabled before they are defined in this file!)
+
+# NONE
+
# Note that PNG_USR_CONFIG only has an effect when building
# pnglibconf.h
setting API_RULE default 0
+# This allows a prefix to be added to the front of every API functon name (and
+# therefore every symbol) by redefining all the function names with the prefix
+# at the end of pnglibconf.h. It also turns on similar internal symbol renaming
+# by causing a similar build-time only file, pngprefix.h, to be generated.
+
+setting PREFIX
+
# Default to using the read macros
setting DEFAULT_READ_MACROS default 1
+# These settings configure the default compression level (0-9) and 'strategy';
+# strategy is as defined by the implementors of zlib, it describes the input
+# data and modifies the zlib parameters in an attempt to optimize the balance
+# between search and huffman encoding in the zlib algorithms. The defaults are
+# the zlib.h defaults - the apparently recursive definition does not arise
+# because the name of the setting is prefixed by PNG_
+#
+# The TEXT values are the defaults when writing compressed text (all forms)
+
+setting Z_DEFAULT_COMPRESSION default Z_DEFAULT_COMPRESSION
+setting Z_DEFAULT_STRATEGY default Z_FILTERED
+setting Z_DEFAULT_NOFILTER_STRATEGY default Z_DEFAULT_STRATEGY
+
+setting TEXT_Z_DEFAULT_COMPRESSION default Z_DEFAULT_COMPRESSION
+setting TEXT_Z_DEFAULT_STRATEGY default Z_DEFAULT_STRATEGY
+
# The alternative is to call functions to read PNG values, if
# the functions are turned *off* the read macros must always
# be enabled, so turning this off will actually force the
option WRITE_INT_FUNCTIONS disabled
option WRITE enables WRITE_INT_FUNCTIONS
-# Generic options - affect both read and write.
+# Error controls
+#
+# WARNINGS: normally on, if off no warnings are generated
+# ERROR_TEXT: normally on, if off errors happen but there is no message
+# ERROR_NUMBERS: unimplemented feature, therefore disabled
+# BENIGN_ERRORS: support for just issuing warnings for recoverable errors
+#
+# BENIGN_READ_ERRORS:
+# By default recoverable errors on read should just generate warnings,
+# generally safe but PNG files that don't conform to the specification will
+# be accepted if a meaningful result can be produced.
+#
+# BENIGN_WRITE_ERRORS:
+# By default recoverable errors on write should just generate warnings,
+# not generally safe because this allows the application to write invalid
+# PNG files. Applications should enable this themselves; it's useful
+# because it means that a failure to write an ancilliary chunk can often be
+# ignored.
option WARNINGS
+option ERROR_TEXT
+option ERROR_NUMBERS disabled
+
option BENIGN_ERRORS
+option BENIGN_WRITE_ERRORS requires BENIGN_ERRORS disabled
+option BENIGN_READ_ERRORS requires BENIGN_ERRORS
+
+
+# Generic options - affect both read and write.
+
option MNG_FEATURES
# Arithmetic options, the first is the big switch that chooses between internal
option FLOATING_POINT enables ok_math
option FIXED_POINT enables ok_math
-# Added at libpng version 1.4.0
-
-option ERROR_TEXT
-
# The following is always on (defined empty)
setting CALLOC_SUPPORTED default
option SETJMP
= NO_SETJMP SETJMP_NOT_SUPPORTED
-# For the moment this is disabled (no code support):
-
-option ERROR_NUMBERS disabled
-
# If this is disabled it is not possible for apps to get the
# values from the 'info' structure, this effectively removes
# quite a lot of the READ API.
# See the comments above about how to change options and settings.
# READ options
+#
+# WARNING: in libpng 1.5 maintained configuration compatibility with earlier
+# versions. In some cases turning off an option turned off other options, in
+# others it was ineffective unless dependent options were also turned off.
+# Libpng 1.6 changes this: in general if you turn off an option that affects
+# APIs it stays off and simply disables APIs that depend on it.
+#
+# As a result if you simply port the libpng 1.5 configuration to libpng 1.6 you
+# will probably see build failures due to missing APIs. Fixing these failures
+# requires some, perhaps considerable, knowledge of what your libpng using
+# applications are doing, fortunately there is no great reason for you to move
+# to libpng 1.6; the new interfaces in 1.6 will take several years to become
+# popular.
option READ enables READ_INTERLACING
option READ_TRANSFORMS requires READ
= NO_READ_TRANSFORMS READ_TRANSFORMS_NOT_SUPPORTED
-option READ_EXPAND requires READ_TRANSFORMS
-option READ_EXPAND_16 requires READ_TRANSFORMS READ_16BIT enables READ_EXPAND
-option READ_SHIFT requires READ_TRANSFORMS
-option READ_PACK requires READ_TRANSFORMS
+# Read gamma handling. Gamma processing is a core part of libpng and many of
+# the capabilities are dependent on libpng performing gamma correction.
+#
+# In libpng 1.6 disabling gamma processing (setting PNG_NO_READ_GAMMA)
+# consistently disables those parts of the API that depend on it. Prior to
+# 1.6.0 this was not true; the results were unpredictable and varied between
+# releases.
+#
+# If you disable gamma processing and your program no longer compiles you need
+# to ask whether you really need the APIs that are missing. If you do then you
+# almost certainly need the gamma processing.
+#
+# If you handle gamma issues outside libpng then you do not need the libpng
+# gamma processing; and it is an enormous waste of space. You just need to
+# remove the use of libpng APIs that depend on it.
+option READ_GAMMA requires READ_TRANSFORMS READ_gAMA
+
+option READ_ALPHA_MODE requires READ_TRANSFORMS READ_GAMMA
+option READ_BACKGROUND requires READ_TRANSFORMS READ_STRIP_ALPHA READ_GAMMA
option READ_BGR requires READ_TRANSFORMS
-option READ_SWAP requires READ_TRANSFORMS READ_16BIT
-option READ_PACKSWAP requires READ_TRANSFORMS
-option READ_INVERT requires READ_TRANSFORMS
-option READ_BACKGROUND requires READ_TRANSFORMS enables READ_STRIP_ALPHA
-option READ_STRIP_16_TO_8 requires READ_TRANSFORMS
-option READ_SCALE_16_TO_8 requires READ_TRANSFORMS
+option READ_EXPAND_16 requires READ_TRANSFORMS READ_16BIT READ_EXPAND
+option READ_EXPAND requires READ_TRANSFORMS
option READ_FILLER requires READ_TRANSFORMS
-option READ_GAMMA requires READ_TRANSFORMS enables READ_gAMA
option READ_GRAY_TO_RGB requires READ_TRANSFORMS
-
-option READ_ALPHA_MODE requires READ_TRANSFORMS enables READ_GAMMA
-option READ_SWAP_ALPHA requires READ_TRANSFORMS
option READ_INVERT_ALPHA requires READ_TRANSFORMS
+option READ_INVERT requires READ_TRANSFORMS
+option READ_PACK requires READ_TRANSFORMS
+option READ_PACKSWAP requires READ_TRANSFORMS
+option READ_RGB_TO_GRAY requires READ_TRANSFORMS READ_GAMMA
+option READ_SCALE_16_TO_8 requires READ_TRANSFORMS
+option READ_SHIFT requires READ_TRANSFORMS
+option READ_STRIP_16_TO_8 requires READ_TRANSFORMS
option READ_STRIP_ALPHA requires READ_TRANSFORMS
+option READ_SWAP_ALPHA requires READ_TRANSFORMS
+option READ_SWAP requires READ_TRANSFORMS READ_16BIT
option READ_USER_TRANSFORM requires READ_TRANSFORMS
-option READ_RGB_TO_GRAY requires READ_TRANSFORMS
option PROGRESSIVE_READ requires READ
option SEQUENTIAL_READ requires READ
option BUILD_GRAYSCALE_PALETTE
-# IN DEVELOPMENT
-# These are currently experimental features; define them if you want
-
-# NOTHING HERE
-
# WRITE options
option WRITE
# API is implemented, they get recorded in pnglibconf.h, but
# can't be changed by the application.
-# Check the correctness of cHRM chunks
+# Colorspace support (enabled as required); just the support for colorant
+# information. Gamma support, likewise, is just support for the gamma
+# information, READ_GAMMA is required for gamma transformations (so it
+# is possible to read PNG gamma without enabling all the libpng transform
+# code - do this for applications that do their own gamma processing)
+#
+# As of 1.6.0 COLORSPACE is only useful if the application processes the
+# information; this is because the library does not do any colorspace
+# processing, it just validates the data in the PNG file.
-option CHECK_cHRM requires cHRM
+option GAMMA disabled
+option COLORSPACE enables GAMMA disabled
+# When an ICC profile is read, or png_set, it will be checked for a match
+# against known sRGB profiles if the sRGB handling is enabled. This
+# setting controls how much work is done during the check:
+#
+# 0: Just validate the profile MD5 signature if present, otherwise use
+# the checks in option 1.
+#
+# 1: Additionally check the length, intent and adler32 checksum of the
+# actual data. If enabled this will reject known profiles that have
+# had the rendering intent in the header changed as well as other edits
+# done without updating the checksum. See the discussion below.
+#
+# 2: Additionally checksum all the data using the ethernet CRC32 algorithm.
+# This makes it more difficult to fake profiles and makes it less likely
+# to get a false positive on profiles with no signature, but is probably
+# just a waste of time since all currently approved ICC sRGB profiles have
+# a secure MD5 signature.
+#
+# The rendering intent. An ICC profile stores an intended rendering intent,
+# but does not include the value in the signature. The intent is documented
+# as the intent that should be used when combining two profiles. The sRGB
+# profile is intended, however, to be used with any of the four defined intents.
+# For this reason the sRGB chunk includes an 'intent' to be used when displaying
+# the image (intent is really a property of the image not the profile.)
+#
+# Unfortunately the iCCP chunk does not. It may therefore be that some
+# applications modify the intent in profiles (including sRGB profiles) to work
+# round this problem. Selecting an option other than option '0' will cause such
+# modified profiles to be rejected.
#
+# Security. The use of Adler32 and CRC32 checksums does not help significantly
+# with any security issues. It is relatively easy to produce arbitrary profiles
+# with the required checksums on current computer systems. Nevertheless
+# security does not seem to be an issue because the only consequence of a false
+# positive is a false assertion that the profile is an sRGB profile. This might
+# be used to hide data from libpng using applications, but it doesn't seem
+# possible to damage them.
+
+setting sRGB_PROFILE_CHECKS default 2
+
# Artificially align memory - the code typically aligns to 8 byte
# boundaries if this is switched on, it's a small waste of space
# but can help (in theory) on some architectures. Only affects
setting ZBUF_SIZE default 8192
+# This is the size of the decompression buffer used when counting or checking
+# the decompressed size of an LZ stream from a compressed ancilliary chunk; the
+# decompressed data is never used so a different size may be optimal. This size
+# was determined using contrib/libtests/timepng.c with compressed zTXt data
+# around 11MByte in size. Slight speed improvements (up to about 14% in
+# timepng) can be achieved by very large increases (to 32kbyte) on regular data,
+# but highly compressible data shows only around 2% improvement. The size is
+# chosen to minimize the effects of DoS attacks based on using very large
+# amounts of highly compressible data.
+
+setting INFLATE_BUF_SIZE default 1024
+
+# This is the maximum amount of IDAT data that the sequential reader will
+# process at one time. The setting does not affect the size of IDAT chunks
+# read, just the amount read at once. Neither does it affect the progressive
+# reader, which processes just the amount of data the application gives it.
+# The sequential reader is currently unable to process more than one IDAT at
+# once - it has to read and process each one in turn. There is no point setting
+# this to a value larger than the IDAT chunks typically encountered (it would
+# just waste memory) but there may be some point in reducing it below the value
+# of ZBUF_SIZE (the size of IDAT chunks written by libpng.)
+
+setting IDAT_READ_SIZE default PNG_ZBUF_SIZE
+
# Ancillary chunks
chunk bKGD
-chunk cHRM
-chunk gAMA
+chunk cHRM enables COLORSPACE
+chunk gAMA enables GAMMA
chunk hIST
-chunk iCCP
+chunk iCCP enables COLORSPACE GAMMA
chunk iTXt
chunk oFFs
chunk pCAL
-chunk sCAL
chunk pHYs
chunk sBIT
+chunk sCAL
chunk sPLT
-chunk sRGB
+chunk sRGB enables COLORSPACE GAMMA
chunk tEXt requires TEXT
chunk tIME
chunk tRNS
option READ_OPT_PLTE requires READ_ANCILLARY_CHUNKS
-option READ_UNKNOWN_CHUNKS requires READ
-option READ_UNKNOWN_CHUNKS enables UNKNOWN_CHUNKS READ_USER_CHUNKS
-option READ_USER_CHUNKS requires READ enables USER_CHUNKS
+# Unknown chunk handling
+#
+# 'UNKNOWN_CHUNKS' is a global option to disable all unknown chunk handling on
+# read or write; everything else below requires it (directly or indirectly).
+option UNKNOWN_CHUNKS
+
+# There are three main options to control the ability to read and write unknown
+# chunks. If either read option is turned on then unknown chunks will be read,
+# otherwise they are skipped. If the write option is turned on unknown chunks
+# set by png_set_unknown_chunks will be written otherwise it is an error to call
+# that API on a write struct.
+option WRITE_UNKNOWN_CHUNKS requires WRITE requires UNKNOWN_CHUNKS
+option WRITE_UNKNOWN_CHUNKS enables STORE_UNKNOWN_CHUNKS
+
+# The first way to read user chunks is to have libpng save them for a later call
+# to png_get_unknown_chunks, the application must call
+# png_set_keep_unknown_chunks to cause this to actually happen (see png.h)
+option SAVE_UNKNOWN_CHUNKS requires READ requires SET_UNKNOWN_CHUNKS
+option SAVE_UNKNOWN_CHUNKS enables READ_UNKNOWN_CHUNKS STORE_UNKNOWN_CHUNKS
+
+# The second approach is to use an application provided callback to process the
+# chunks, the callback can either handle the chunk entirely itself or request
+# that libpng store the chunk for later retrieval via png_get_unknown_chunks.
+#
+# Note that there is no 'WRITE_USER_CHUNKS' so the USER_CHUNKS option is always
+# the same as READ_USER_CHUNKS at present
+option READ_USER_CHUNKS requires READ requires UNKNOWN_CHUNKS
+option READ_USER_CHUNKS enables READ_UNKNOWN_CHUNKS USER_CHUNKS
+
+# Two further options are provided to allow detailed control of the handling.
+# The first enables png_set_keep_unknown_chunks; this allows the default to be
+# changed from discarding unknown chunks and allows per-chunk control. This is
+# required to use the SAVE_UNKNOWN_CHUNKS option. If enabled this option also
+# applies to write (see png.h), otherwise the write API simply writes all the
+# chunks it is given.
+#
+# The second option extends the unknown handling to allow known chunks to be
+# handled as though they were unknown. This option doesn't change any APIs, it
+# merely turns on the code to check known as well as unknown chunks.
+#
+# This option no longer affects the write code. It can be safely disabled and
+# will prevent applications stopping libpng reading known chunks.
+option SET_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS
+option HANDLE_AS_UNKNOWN requires SET_UNKNOWN_CHUNKS
+
+# The following options are derived from the above and should not be turned on
+# explicitly.
+option READ_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
+option STORE_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
option CONVERT_tIME requires WRITE_ANCILLARY_CHUNKS
# The "tm" structure is not supported on WindowsCE
option WRITE_FILTER requires WRITE
-option WRITE_UNKNOWN_CHUNKS requires WRITE
-
-option HANDLE_AS_UNKNOWN
-
-option SAVE_INT_32 requires WRITE
-
-# png_save_int_32 is required by the ancillary chunks oFFs and pCAL
+option SAVE_INT_32 disabled
+# png_save_int_32 is required internally for writing the ancillary chunks oFFs
+# and pCAL and for both reading and writing iCCP (for the generation/checking of
+# the corresponding cHRM/gAMA chunks) if full ICC is supported.
# added at libpng-1.5.4
option READ_CHECK_FOR_INVALID_INDEX requires READ CHECK_FOR_INVALID_INDEX
option WRITE_CHECK_FOR_INVALID_INDEX requires WRITE CHECK_FOR_INVALID_INDEX
+# added at libpng-1.5.15
+option GET_PALETTE_MAX enables READ_GET_PALETTE_MAX WRITE_GET_PALETTE_MAX
+option READ_GET_PALETTE_MAX requires READ_CHECK_FOR_INVALID_INDEX disabled
+option WRITE_GET_PALETTE_MAX requires WRITE_CHECK_FOR_INVALID_INDEX disabled
+
+# Simplified API options (added at libpng-1.6.0)
+# Read:
+option SIMPLIFIED_READ requires SEQUENTIAL_READ READ_TRANSFORMS SETJMP
+option SIMPLIFIED_READ requires BENIGN_ERRORS READ_GAMMA
+option SIMPLIFIED_READ enables READ_EXPAND READ_16BIT READ_EXPAND_16
+option SIMPLIFIED_READ enables READ_SCALE_16_TO_8 READ_RGB_TO_GRAY
+option SIMPLIFIED_READ enables READ_ALPHA_MODE READ_BACKGROUND READ_STRIP_ALPHA
+option SIMPLIFIED_READ enables READ_FILLER READ_SWAP
+
+option SIMPLIFIED_READ_AFIRST requires SIMPLIFIED_READ disabled
+option READ_SWAP_ALPHA enables SIMPLIFIED_READ_AFIRST
+
+option SIMPLIFIED_READ_BGR requires SIMPLIFIED_READ disabled
+option READ_BGR enables SIMPLIFIED_READ_BGR
+
+# Write:
+option SIMPLIFIED_WRITE requires WRITE STDIO SETJMP
+option SIMPLIFIED_WRITE enables WRITE_SWAP WRITE_gAMA WRITE_sRGB WRITE_cHRM
+
+option SIMPLIFIED_WRITE_AFIRST requires SIMPLIFIED_WRITE disabled
+option WRITE_SWAP_ALPHA enables SIMPLIFIED_WRITE_AFIRST
+
+option SIMPLIFIED_WRITE_BGR requires SIMPLIFIED_WRITE disabled
+option WRITE_BGR enables SIMPLIFIED_WRITE_BGR
+
+# Formats:
+option FORMAT_AFIRST if SIMPLIFIED_READ_AFIRST SIMPLIFIED_WRITE_AFIRST
+option FORMAT_BGR if SIMPLIFIED_READ_BGR SIMPLIFIED_WRITE_BGR
projects / l4.git / blobdiff