This rewrites the code used previously in the heuristics to make it easier to
debug and introduces the 'methodical' method, which is intended to be an
expensive but reliable way of reducing image size.
The code in this commit does not work; the 'methodical' test for success does
not take account of data buffered inside zlib and, anyway, it changes the
results of pngtest so that the test fails. This commit is just a checkpoint of
the current state; another commit will temporarily disable the 'methodical'
code.
Signed-off-by: John Bowler <jbowler@acm.org>
Undefined because (png_byte) << shift is undefined if it changes the signed bit
(because png_byte is promoted to int). The libpng exported functions
png_get_uint_32 and png_get_uint_16 handle this.
Bug reported by David Drysdale as a result of reports from UBSAN in clang 3.8.
This changes pngvalid to use BE random numbers; this used to produce errors but
these should not be fixed as a result of the previous changes.
Signed-off-by: John Bowler <jbowler@acm.org>
This widens the 'limit' check on the internally calculated error limits in the
'DIGITIZE' case (the code used prior to 1.7 for rgb_to_gray error checks) and it
changes the check to only operate in non-release builds (base build type not RC
or RELEASE.)
Signed-off-by: John Bowler <jbowler@acm.org>
Fixes to pngvalid for various reduced build configurations (eliminate unused
statics) and a fix for the case in rgb_to_gray when the digitize option reduces
graylo to 0, producing a large error.
Signed-off-by: John Bowler <jbowler@acm.org>
This 'fixes' the current problem in the BE tests by not testing it, making the
BE code the same as the LE version.
Signed-off-by: John Bowler <jbowler@acm.org>
The filter selection options are made more intuitive (IMO, but I am not an
Intuitive User). Dummy code added for methodical filter selection.
Signed-off-by: John Bowler <jbowler@acm.org>
This implements the heuristic part of filter selction, the methodic testing
approach is still not implemented. png_set_option methods are incomplete.
Signed-off-by: John Bowler <jbowler@acm.org>
This removes the side-effect on the png_struct palette of calling png_set_PLTE
or png_set_tRNS. NOTE: this is a quiet API change, it was possible before to
alter the palette on a PNG image by using png_set_PLTE, but this was unintended
and inconsistent with the other png_set APIs.
Fix a bug in palette index checking; png_struct::num_palette could, in
principle, get changed by the transformations (e.g. png_set_quantize) and this
would invalidate the check. The palette checking init function now makes a copy
of png_struct::num_palette.
Fix a bug in pngvalid error handling. A png_error in png_write_info is not
continuable (a valid image cannot necessarily be written afterward) because the
png_error aborts the write of subsequent pre-IDAT chunks. In particular an
abort as a result of a bogus colorspace information (gAMA, cHRM, sBIT etc)
prevents the write of the PLTE chunk.
Signed-off-by: John Bowler <jbowler@acm.org>
Unify the compression code so that inflate calls are localized to a common
routine. Ground work for filter selection support. Minor API changes to use
void* not byte* for data parameters. Unification of some of the compression
code with the decompression code; IDAT_size replaces IDAT_read_size and
zbuffer_size, IDAT reading and writing is no longer controlled by the size of
the compression buffer.
Signed-off-by: John Bowler <jbowler@acm.org>
