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Fix issue whereby libjpeg-turbo would report "fractional sampling not implemented" when attempting to use decompression scaling with a non-power-of-2 scaling ratio and a JPEG file that was compressed using an odd form of subsampling, such as 3x2.

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git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@774 632fc199-4ca6-4c93-a231-07263d6284db
This commit is contained in:
DRC
2012-02-03 06:55:26 +00:00
parent 3ee09f164f
commit a12d14eb90
1 changed files with 5 additions and 5 deletions
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10
jdmaster.c
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@@ -285,16 +285,16 @@ jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
/* In selecting the actual DCT scaling for each component, we try to
* scale up the chroma components via IDCT scaling rather than upsampling.
* This saves time if the upsampler gets to use 1:1 scaling.
* Note this code assumes that the supported DCT scalings are powers of 2.
* Note this code adapts subsampling ratios which are powers of 2.
*/
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
ci++, compptr++) {
int ssize = cinfo->_min_DCT_scaled_size;
while (ssize < DCTSIZE &&
(compptr->h_samp_factor * ssize * 2 <=
cinfo->max_h_samp_factor * cinfo->_min_DCT_scaled_size) &&
(compptr->v_samp_factor * ssize * 2 <=
cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size)) {
((cinfo->max_h_samp_factor * cinfo->_min_DCT_scaled_size) %
(compptr->h_samp_factor * ssize * 2) == 0) &&
((cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size) %
(compptr->v_samp_factor * ssize * 2) == 0)) {
ssize = ssize * 2;
}
#if JPEG_LIB_VERSION >= 70