READ_GAMMA. Prior to 1.6.0 switching off READ_GAMMA did unpredictable things
to the interfaces that use it (specifically, png_do_background in 1.4 would
simply display composite for grayscale images but do composition
with the incorrect arithmetic for color ones). In 1.6 the semantic
of -DPNG_NO_READ_GAMMA is changed to simply disable any interface that
depends on it; this obliges people who set it to consider whether they
really want it off if they happen to use any of the interfaces in
question (typically most users who disable it won't).
management system (CMS). In practice it is not possible to obtain cHRM
information reliably using just the end-point tags because they do not exist
in the vast majority of profiles. Instead it is necessary to run the endpoints
through the ICC colorimetric intent transform (as described in the v4
spec). Since this is likely to be too much code inside libpng for too
little gain (it implies a fairly complete CMS implementation) the code
has been changed to allow an external CMS to be used. This code is
temporarily disabled until a suitable set of test cases using one or more
external CMS implementations have been implemented.
type rules. By the ANSI-C standard the new types should be identical to the
previous versions, and all known versions of gcc tested with the previous
versions except for GCC-4.2.1 work with this version. The change makes the
ANSI-C rule that const applied to an array of elements applies instead to the
elements in the array moot by explicitly applying const to the base
elements of the png_icc_matrix and png_icc_vector types. The accidental
(harmless) 'const' previously applied to the parameters of two of the
functions have also been removed.
Glenn thought the "adopted" were typos and changed them all to "adapted".
This reverts the spelling and adds parenthetical comments when each
word first appears in png.h.
fixed Cygwin+MSVC build errors. The ICC profile handling now includes more
checking. Several errors that caused rejection of the profile are now
handled with a warning in such a way that the invalid profiles will be
read by default in release (but not pre-RC) builds but will not be
written by default. The easy part of handling a cHRM chunk is written,
where the ICC profile contains the required data. The more difficult
part plus guessing a gAMA value requires code to pass selected RGB values
through the profile.
option to pngtest. The "--relaxed" option turns off the benign errors that are
enabled by default in pre-RC builds. makepng can now write ICC profiles
where the length has not been extended to a multiple of 4, and pngtest
now intercepts all libpng errors, allowing the previously-introduced
"--strict test" on no warnings to actually work.
contrib/libtests/makepng: corrected 'rgb' and 'gray' cases. profile_error
messages could be truncated; made a correct buffer size calculation and
adjusted pngerror.c appropriately. png_icc_check_* checking improved;
changed the functions to receive the correct color type of the PNG on read
or write and check that it matches the color space of the profile (despite
what the comments said before, there is danger in assuming the app will
cope correctly with an RGB profile on a grayscale image and, since it
violates the PNG spec, allowing it is certain to produce inconsistent
app behavior and might even cause app crashes.) Check that profiles
contain the tags needed to process the PNG (tags all required by the ICC
spec). Removed unused PNG_STATIC from pngpriv.h.
png_handle_unknown() when SAVE support is absent. Moved the shell test
scripts for contrib/libtests from the libpng top directory to contrib/libtests.
png_handle_unknown() must always read or skip the chunk, if
SAVE_UNKNOWN_CHUNKS is turned off *and* the application does not set
a user callback an unknown chunk will not be read, leading to a read
error, which was revealed by the "tunknown" test.
libpng handling of unknown chunks other than vpAg and sTER (including
unsafe-to-copy chunks which were dropped before) and eliminates the
repositioning of vpAg and sTER in pngtest.png by changing pngtest.png
(so the chunks are where libpng would put them).
png_set_keep_unknown_chunks() to be turned off if not required and causes
both read and write to behave appropriately (on read this is only possible
if the user callback is used to handle unknown chunks). The change
also removes the support for storing unknown chunks in the info_struct
if the only unknown handling enabled is via the callback, allowing libpng
to be configured with callback reading and none of the unnecessary code.
control of the unknown handling, corrects the pre-existing bug where
the per-chunk 'keep' setting is ignored and makes it possible to skip
IDAT chunks in the sequential reader (broken in earlier 1.6 versions).
There is a new test program, test-unknown.c, which is a work in progress
(not currently part of the test suite). Comments in the header files now
explain how the unknown handling works.
support. Now "make check" will succeed even if libpng is compiled with
-DPNG_NO_READ or -DPNG_NO_WRITE. The tests performed are reduced, but the
basic reading and writing of a PNG file is always tested by one or more of
the tests.
errors) and cause it not to fail at the comparison step if libpng lacks support
for writing chunks that it reads from the input (currently only implemented
for compressed text chunks).
