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Make png_struct palette, trans_alpha private

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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>
This commit is contained in:
John Bowler
2015-12-01 08:16:53 -08:00
parent 8fe2eac47f
commit 84a8bb8244
8 changed files with 137 additions and 139 deletions
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22
pngset.c
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@@ -533,30 +533,20 @@ png_set_PLTE(png_structrp png_ptr, png_inforp info_ptr,
png_error(png_ptr, "Invalid palette");
#endif /* MNG_FEATURES */
/* It may not actually be necessary to set png_ptr->palette here;
* we do it for backward compatibility with the way the png_handle_tRNS
* function used to do the allocation.
*
* 1.6.0: the above statement appears to be incorrect; something has to set
* the palette inside png_struct on read.
*/
png_free_data(png_ptr, info_ptr, PNG_FREE_PLTE, 0);
/* Changed in libpng-1.2.1 to allocate PNG_MAX_PALETTE_LENGTH instead
* of num_palette entries, in case of an invalid PNG file or incorrect
* call to png_set_PLTE() with too-large sample values.
*/
png_ptr->palette = png_voidcast(png_colorp, png_calloc(png_ptr,
info_ptr->palette = png_voidcast(png_colorp, png_calloc(png_ptr,
PNG_MAX_PALETTE_LENGTH * (sizeof (png_color))));
if (num_palette > 0)
memcpy(png_ptr->palette, palette, num_palette * (sizeof (png_color)));
info_ptr->palette = png_ptr->palette;
info_ptr->num_palette = png_ptr->num_palette = png_check_bits(png_ptr,
num_palette, 9);
memcpy(info_ptr->palette, palette, num_palette * (sizeof (png_color)));
info_ptr->num_palette = png_check_bits(png_ptr, num_palette, 9);
info_ptr->free_me |= PNG_FREE_PLTE;
info_ptr->valid |= PNG_INFO_PLTE;
}
@@ -962,11 +952,11 @@ png_set_tRNS(png_structrp png_ptr, png_inforp info_ptr,
/* Expect png_set_PLTE to happen before png_set_tRNS, so num_palette will
* be set, but this is not a requirement of the API.
*/
if (png_ptr->num_palette)
max_num = png_ptr->num_palette;
if (info_ptr->num_palette)
max_num = info_ptr->num_palette;
else
max_num = 1 << png_ptr->bit_depth;
max_num = 1 << info_ptr->bit_depth;
if (num_trans > max_num)
{