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[libpng15] Fixes to alpha swap on read, simplified write and filler add code

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This commit is contained in:
John Bowler
2011-11-08 21:35:16 -06:00
committed by Glenn Randers-Pehrson
parent d4973837b2
commit e6fb691c49
3 changed files with 46 additions and 21 deletions
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28
pngread.c
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@@ -1804,10 +1804,12 @@ png_image_read_end(png_voidp argument)
else /* output needs an alpha channel */
{
/* This is tricky because it happens before the swap operation has
* been accomplished, so always add the alpha channel after the
* component channels.
* been accomplished however the swap does *not* swap the added
* alpha channel (weird API), so it must be added in the correct
* place.
*/
png_uint_32 filler; /* opaque filler */
int where;
if (linear)
filler = 65535;
@@ -1815,9 +1817,21 @@ png_image_read_end(png_voidp argument)
else
filler = 255;
png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
{
where = PNG_FILLER_BEFORE;
change &= ~PNG_FORMAT_FLAG_AFIRST;
}
else
# endif
where = PNG_FILLER_AFTER;
png_set_add_alpha(png_ptr, filler, where);
}
/* This stops the (irrelevant) call to swap_alpha below. */
change &= ~PNG_FORMAT_FLAG_ALPHA;
}
@@ -1841,7 +1855,7 @@ png_image_read_end(png_voidp argument)
}
# ifdef PNG_FORMAT_BGR_SUPPORTED
if (format & PNG_FORMAT_FLAG_BGR)
if (change & PNG_FORMAT_FLAG_BGR)
{
/* Check only the output format; PNG is never BGR, don't do this if
* the output is gray, but fix up the 'format' value in that case.
@@ -1857,7 +1871,7 @@ png_image_read_end(png_voidp argument)
# endif
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
if (change & PNG_FORMAT_FLAG_AFIRST)
{
/* Only relevant if there is an alpha channel - it's particularly
* important to handle this correctly because do_local_compose may
@@ -1924,7 +1938,9 @@ png_image_read_end(png_voidp argument)
# endif
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (png_ptr->transformations & PNG_SWAP_ALPHA)
if (png_ptr->transformations & PNG_SWAP_ALPHA ||
((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
(png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
info_format |= PNG_FORMAT_FLAG_AFIRST;
# endif