mewin/libpng
1
0
Fork 0
mirror of https://git.code.sf.net/p/libpng/code.git synced 2025-07-10 18:04:09 +02:00
Code Issues Projects Releases Wiki Activity

[libpng16] Revised pngvalid to generate size images with as many filters as

Browse Source 
it can manage, limited by the number of rows.
This commit is contained in:
John Bowler
2013-10-17 08:23:13 -05:00
committed by Glenn Randers-Pehrson
parent 681b731151
commit 9e9977e153
4 changed files with 35 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
contrib/libtests/pngvalid.c
View File

@@ -2945,6 +2945,12 @@ sbit_modification_init(sbit_modification *me, png_modifier *pm, png_byte sbit)
* height of 16 rows. The width and height are stored in the FILEID and, being
* non-zero, indicate a size file.
*
* Because the PNG filter code is typically the largest CPU consumer within
* libpng itself there is a tendency to attempt to optimize it. This results in
* special case code which needs to be validated. To cause this to happen the
* 'size' images are made to use each possible filter, in so far as this is
* possible for smaller images.
*
* For palette image (colour type 3) multiple transform images are stored with
* the same bit depth to allow testing of more colour combinations -
* particularly important for testing the gamma code because libpng uses a
@@ -3660,6 +3666,7 @@ make_size_image(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
int npasses = npasses_from_interlace_type(pp, interlace_type);
png_uint_32 y;
int pass;
int nfilter = PNG_FILTER_VALUE_LAST;
png_byte image[16][SIZE_ROWMAX];
/* To help consistent error detection make the parts of this buffer
@@ -3713,7 +3720,22 @@ make_size_image(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
continue;
}
/* Only get to here if the row has some pixels in it. */
/* Only get to here if the row has some pixels in it, set the
* filters to 'all' for the very first row and thereafter to a
* single filter. It isn't well documented, but png_set_filter
* 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.
*/
png_set_filter(pp, 0/*method*/,
nfilter >= PNG_FILTER_VALUE_LAST ? PNG_ALL_FILTERS : nfilter);
if (nfilter-- == 0)
nfilter = PNG_FILTER_VALUE_LAST-1;
png_write_row(pp, row);
}
}