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Better filter checking

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Improve pngvalid coverage of filter combinations, remove the (new in 1.7) code
which disabled previous-row filters on the first row of an image in some cases.

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler
2015-11-24 22:24:18 -08:00
parent 8bffb48bc1
commit 1775bdeb24
2 changed files with 46 additions and 107 deletions
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60
contrib/libtests/pngvalid.c
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@@ -276,7 +276,8 @@ make_four_random_bytes(png_uint_32* seed, png_bytep bytes)
make_random_bytes(seed, bytes, 4);
}
#if defined PNG_READ_SUPPORTED || defined PNG_WRITE_tRNS_SUPPORTED
#if defined PNG_READ_SUPPORTED || defined PNG_WRITE_tRNS_SUPPORTED ||\
defined PNG_WRITE_FILTER_SUPPORTED
static void
randomize(void *pv, size_t size)
{
@@ -285,7 +286,7 @@ randomize(void *pv, size_t size)
}
#define RANDOMIZE(this) randomize(&(this), sizeof (this))
#endif /* READ || WRITE_tRNS */
#endif /* READ || WRITE_tRNS || WRITE_FILTER */
#ifdef PNG_READ_TRANSFORMS_SUPPORTED
static unsigned int
@@ -309,8 +310,8 @@ random_choice(void)
return x & 1;
}
#endif
#endif /* PNG_READ_SUPPORTED */
#endif /* READ_RGB_TO_GRAY || READ_FILLER */
#endif /* READ_TRANSFORMS */
/* A numeric ID based on PNG file characteristics. The 'do_interlace' field
* simply records whether pngvalid did the interlace itself or whether it
@@ -3649,6 +3650,31 @@ deinterlace_row(png_bytep buffer, png_const_bytep row,
* layout details. See make_size_images below for a way to make images
* that test odd sizes along with the libpng interlace handling.
*/
#ifdef PNG_WRITE_FILTER_SUPPORTED
static void
choose_random_filter(png_structp pp, int start)
{
/* Choose filters randomly except that on the very first row ensure that
* there is at least one previous row filter.
*/
int filters;
RANDOMIZE(filters);
filters &= PNG_ALL_FILTERS;
/* There may be no filters; skip the setting. */
if (filters != 0)
{
if (start && filters < PNG_FILTER_UP)
filters |= PNG_FILTER_UP;
png_set_filter(pp, 0/*method*/, filters);
}
}
#else /* !WRITE_FILTER */
# define choose_random_filter(pp, start) ((void)0)
#endif /* !WRITE_FILTER */
static void
make_transform_image(png_store* const ps, png_byte const colour_type,
png_byte const bit_depth, unsigned int palette_number,
@@ -3767,6 +3793,7 @@ make_transform_image(png_store* const ps, png_byte const colour_type,
}
# endif /* do_own_interlace */
choose_random_filter(pp, pass == 0 && y == 0);
png_write_row(pp, buffer);
}
}
@@ -3943,9 +3970,6 @@ make_size_image(png_store* const ps, png_byte const colour_type,
int npasses = npasses_from_interlace_type(pp, interlace_type);
png_uint_32 y;
int pass;
# ifdef PNG_WRITE_FILTER_SUPPORTED
int nfilter = PNG_FILTER_VALUE_LAST;
# endif
png_byte image[16][SIZE_ROWMAX];
/* To help consistent error detection make the parts of this buffer
@@ -4008,15 +4032,23 @@ make_size_image(png_store* const ps, png_byte const colour_type,
* does accept a filter number (per the spec) as well as a bit
* mask.
*
* The apparent wackiness of decrementing nfilter rather than
* incrementing is so that Paeth gets used in all images bigger
* than 1 row - it's the tricky one.
* The code now uses filters at random, except that on the first
* row of an image it ensures that a previous row filter is in
* the set so that libpng allocates the row buffer.
*/
png_set_filter(pp, 0/*method*/,
nfilter >= PNG_FILTER_VALUE_LAST ? PNG_ALL_FILTERS : nfilter);
{
int filters;
RANDOMIZE(filters);
filters %= PNG_FILTER_VALUE_LAST;
if (filters < 0) filters = -filters;
filters = 8 << filters;
if (nfilter-- == 0)
nfilter = PNG_FILTER_VALUE_LAST-1;
if (pass == 0 && y == 0 && filters < PNG_FILTER_UP)
filters |= PNG_FILTER_UP;
png_set_filter(pp, 0/*method*/, filters);
}
# endif
png_write_row(pp, row);