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Fix png_set_tRNS_to_alpha for low-bit-depth gray

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Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler 2015-09-25 16:22:17 -07:00
parent 1e563f689c
commit 53e537439f
1 changed files with 10 additions and 7 deletions
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17
pngrtran.c
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@ -776,7 +776,7 @@ fill_transparent_pixel(png_const_structrp png_ptr, png_byte *trans)
#ifdef PNG_READ_EXPAND_SUPPORTED
/* Flags for png_init_expand */
#define PNG_EXPAND_PALETTE 1U /* palette images only, includes tRNS */
#define PNG_EXPAND_LBP_GRAY 2U /* grayscale low-bit depth only */
#define PNG_EXPAND_LBD_GRAY 2U /* grayscale low-bit depth only */
#define PNG_EXPAND_tRNS 4U /* non-palette images only */
/* This struct is only required for tRNS matching, but it is convenient to
@ -1053,7 +1053,7 @@ png_init_expand(png_transformp *transform, png_transform_controlp tc)
debug(tc->init);
if (bit_depth >= 8U)
args &= PNG_BIC_MASK(PNG_EXPAND_LBP_GRAY);
args &= PNG_BIC_MASK(PNG_EXPAND_LBD_GRAY);
# ifdef PNG_READ_tRNS_SUPPORTED
if (png_ptr->num_trans == 0U ||
@ -1066,7 +1066,7 @@ png_init_expand(png_transformp *transform, png_transform_controlp tc)
switch (args)
{
case PNG_EXPAND_LBP_GRAY:
case PNG_EXPAND_LBD_GRAY:
tc->bit_depth = 8U;
tc->invalid_info |= PNG_INFO_tRNS;
@ -1075,7 +1075,7 @@ png_init_expand(png_transformp *transform, png_transform_controlp tc)
break;
# ifdef PNG_READ_tRNS_SUPPORTED
case PNG_EXPAND_LBP_GRAY + PNG_EXPAND_tRNS:
case PNG_EXPAND_LBD_GRAY + PNG_EXPAND_tRNS:
tc->bit_depth = 8U;
tc->format |= PNG_FORMAT_FLAG_ALPHA;
tc->invalid_info |= PNG_INFO_tRNS;
@ -1131,7 +1131,7 @@ png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
{
if (png_ptr != NULL)
png_add_transform(png_ptr, sizeof (png_expand), png_init_expand,
PNG_TR_EXPAND)->args |= PNG_EXPAND_LBP_GRAY;
PNG_TR_EXPAND)->args |= PNG_EXPAND_LBD_GRAY;
}
/* Expand paletted images to 8-bit RGB or, if there is a tRNS chunk, RGBA.
@ -1189,9 +1189,12 @@ png_init_alpha(png_transformp *transform, png_transform_controlp tc)
required = 1;
tc->expand_tRNS = 1U;
/* This happens as a result of an explicit API call to
* png_set_tRNS_to_alpha, so expand low-bit-depth gray too:
*/
if (tc->init == PNG_TC_INIT_FORMAT)
png_add_transform(png_ptr, sizeof (png_expand), png_init_expand,
PNG_TR_EXPAND)->args |= PNG_EXPAND_tRNS;
PNG_TR_EXPAND)->args |= PNG_EXPAND_tRNS + PNG_EXPAND_LBD_GRAY;
}
else
@ -2221,7 +2224,7 @@ push_gamma_expand(png_transformp *transform, png_transform_controlp tc,
affirm(tc->init == PNG_TC_INIT_FINAL);
if (tc->bit_depth < 8U) /* low bit gray: expand to 8 bits */
expand = PNG_EXPAND_LBP_GRAY;
expand = PNG_EXPAND_LBD_GRAY;
/* Gamma correction invalidates tRNS, so if it is being expanded and
* alpha is not being stripped expand it now.