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Fix misdisplay of PNG paletted images

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Problem reported by Roland Winkler (Bug#37153).
Derived from a patch suggested by YAMAMOTO Mitsuharu (Bug#37153#62).
* src/image.c (png_get_valid) [WINDOWSNT]:
Do not dynamically link this function.
(png_get_tRNS) [WINDOWSNT && PNG_tRNS_SUPPORTED]:
Dynamically link this function instead.
(png_load_body): Do not assume that every paletted image supplies
only transparency data.  Fix typo in use of transparent_p.
This commit is contained in:
Paul Eggert 2019-08-25 10:01:46 -07:00
parent ae7ab3b6ee
commit 8826beaf00
1 changed files with 25 additions and 9 deletions
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34
src/image.c
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@ -6234,7 +6234,10 @@ DEF_DLL_FN (void, png_read_info, (png_structp, png_infop));
DEF_DLL_FN (png_uint_32, png_get_IHDR,
(png_structp, png_infop, png_uint_32 *, png_uint_32 *,
int *, int *, int *, int *, int *));
DEF_DLL_FN (png_uint_32, png_get_valid, (png_structp, png_infop, png_uint_32));
# ifdef PNG_tRNS_SUPPORTED
DEF_DLL_FN (png_uint_32, png_get_tRNS, (png_structp, png_infop, png_bytep *,
int *, png_color_16p *));
# endif
DEF_DLL_FN (void, png_set_strip_16, (png_structp));
DEF_DLL_FN (void, png_set_expand, (png_structp));
DEF_DLL_FN (void, png_set_gray_to_rgb, (png_structp));
@ -6273,7 +6276,9 @@ init_png_functions (void)
LOAD_DLL_FN (library, png_set_sig_bytes);
LOAD_DLL_FN (library, png_read_info);
LOAD_DLL_FN (library, png_get_IHDR);
LOAD_DLL_FN (library, png_get_valid);
# ifdef PNG_tRNS_SUPPORTED
LOAD_DLL_FN (library, png_get_tRNS);
# endif
LOAD_DLL_FN (library, png_set_strip_16);
LOAD_DLL_FN (library, png_set_expand);
LOAD_DLL_FN (library, png_set_gray_to_rgb);
@ -6304,7 +6309,7 @@ init_png_functions (void)
# undef png_get_IHDR
# undef png_get_io_ptr
# undef png_get_rowbytes
# undef png_get_valid
# undef png_get_tRNS
# undef png_longjmp
# undef png_read_end
# undef png_read_image
@ -6329,7 +6334,7 @@ init_png_functions (void)
# define png_get_IHDR fn_png_get_IHDR
# define png_get_io_ptr fn_png_get_io_ptr
# define png_get_rowbytes fn_png_get_rowbytes
# define png_get_valid fn_png_get_valid
# define png_get_tRNS fn_png_get_tRNS
# define png_longjmp fn_png_longjmp
# define png_read_end fn_png_read_end
# define png_read_image fn_png_read_image
@ -6589,10 +6594,21 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
/* If image contains simply transparency data, we prefer to
construct a clipping mask. */
if (png_get_valid (png_ptr, info_ptr, PNG_INFO_tRNS))
transparent_p = 1;
else
transparent_p = 0;
transparent_p = false;
# ifdef PNG_tRNS_SUPPORTED
png_bytep trans_alpha;
int num_trans;
if (png_get_tRNS (png_ptr, info_ptr, &trans_alpha, &num_trans, NULL)
&& trans_alpha)
{
int i;
for (i = 0; i < num_trans; i++)
if (0 < trans_alpha[i] && trans_alpha[i] < 255)
break;
if (! (i < num_trans))
transparent_p = true;
}
# endif
/* This function is easier to write if we only have to handle
one data format: RGB or RGBA with 8 bits per channel. Let's
@ -6680,7 +6696,7 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
/* Create an image and pixmap serving as mask if the PNG image
contains an alpha channel. */
if (channels == 4
&& !transparent_p
&& transparent_p
&& !image_create_x_image_and_pixmap (f, img, width, height, 1,
&mask_img, 1))
{