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.
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.
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.
on read and write. In libpng 1.6 the two cases can be distinguished and
considerable code cleanup, and extra error checking, is possible. This
makes calls on the write side that have no effect be ignored with a
png_app_error(), which can be disabled in the app using
png_set_benign_errors(), and removes the spurious use of usr_channels
on the read side.
functions [rw]util.c. A new shared keyword check routine was also added
and the 'zbuf' is no longer allocated on progressive read. It is now
possible to call png_inflate() incrementally.
read code now claims and releases png_ptr->zstream, like the write code.
The bug whereby the progressive reader failed to release the zstream
is now fixed, all initialization is delayed, and the code checks for
changed parameters on deflate rather than always calling
deflatedEnd/deflateInit.
those uses of png_memcpy that were doing a simple assignment to assignments
(all those cases where the thing being copied is a non-array C L-value.)
Added some error checking to png_set_*() routines and removed the
reference to the non-exported function png_memcpy() from example.c. Fixed
the Visual C 64-bit build - it requires jmp_buf to be aligned, but it had
become misaligned.
changes alter how the tricky allocation of the initial png_struct and png_info
structures are handled. png_info is now handled in pretty much the same
way as everything else, except that the allocations handle NULL return
silently. png_struct is changed in a similar way on allocation and on
deallocation a 'safety' error handler is put in place (which should never
be required). The error handler itself is changed to permit mismatches
in the application and libpng error buffer size; however, this means a
silent change to the API to return the jmp_buf if the size doesn't match
the size from the libpng compilation; libpng now allocates the memory and
this may fail. Overall these changes result in slight code size
reductions; however, this is a reduction in code that is always executed
so is particularly valuable. Overall on a 64-bit system the libpng DLL
decreases in code size by 1733 bytes. pngerror.o increases in size by
about 465 bytes because of the new functionality.
These changes alter how the tricky allocation of the initial png_struct and
png_info structures are handled. png_info is now handled in pretty much the
same way as everything else, except that the allocations handle NULL return
silently. png_struct is changed in a similar way on allocation and on
deallocation a 'safety' error handler is put in place (which should never
be required). The error handler itself is changed to permit mismatches
in the application and libpng error buffer size; however, this means a
silent change to the API to return the jmp_buf if the size doesn't match
the size from the libpng compilation; libpng now allocates the memory and
this may fail. Overall these changes result in slight code size
reductions; however, this is a reduction in code that is always executed
so is particularly valuable. Overall on a 64-bit system the libpng DLL
decreases in code size by 1733 bytes. pngerror.o increases in size by
about 465 bytes because of the new functionality.
These fixes attend to most of the errors revealed in pngvalid, however doing
the gamma work twice results in inaccuracies that can't be easily fixed.
There is now a warning in the code if this is going to happen.
wrong (high by one) 25% of the time. Dividing by 257 with rounding is
wrong in 128 out of 65536 cases. Getting the right answer all the time
without division is easy.
This was because the attempt to reset the zlib stream in png_write_IDAT
happened after the first IDAT chunk had been deflated - much too late.
In this change internal functions are added to claim/release the z_stream
and, hopefully, make the code more robust. Also deflateEnd checking is
added - previously libpng would ignore an error at the end of the stream.
This change adds internal APIs to allow png_warning messages to have parameters
without requiring the host OS to implelment snprintf. As a side effect the
dependency of the RFC1132 code on stdio is removed and PNG_NO_WARNINGS does
actually work now.
