dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2025-07-13 14:34:33 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

Lossless decoder fix for a special transform order

Browse Source 
Fix the lossless decoder for the case when it has to apply other
inverse transforms before applying Color indexing inverse transform.

The main idea is to make ColorIndexingInverse virtually in-place: we
use the fact that the argb_cache is allocated to accommodate all
*unpacked* pixels of a macro-row, not just *packed* pixels.

Change-Id: I27f11f3043f863dfd753cc2580bc5b36376800c4
This commit is contained in:
Urvang Joshi
2012-08-09 02:44:38 +05:30
committed by Gerrit Code Review
parent 62dd9bb242
commit a0a488554d
2 changed files with 23 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
src/dsp/lossless.c
View File

@ -935,7 +935,7 @@ static void ColorIndexInverseTransform(
uint32_t packed_pixels = 0;
int x;
for (x = 0; x < width; ++x) {
// We need to load fresh 'packed_pixels' once every 'bytes_per_pixels'
// We need to load fresh 'packed_pixels' once every 'pixels_per_byte'
// increments of x. Fortunately, pixels_per_byte is a power of 2, so
// can just use a mask for that, instead of decrementing a counter.
if ((x & count_mask) == 0) packed_pixels = ((*src++) >> 8) & 0xff;
@ -976,7 +976,21 @@ void VP8LInverseTransform(const VP8LTransform* const transform,
ColorSpaceInverseTransform(transform, row_start, row_end, out);
break;
case COLOR_INDEXING_TRANSFORM:
if (in == out && transform->bits_ > 0) {
// Move packed pixels to the end of unpacked region, so that unpacking
// can occur seamlessly.
// Also, note that this is the only transform that applies on
// the effective width of VP8LSubSampleSize(xsize_, bits_). All other
// transforms work on effective width of xsize_.
const int out_stride = (row_end - row_start) * transform->xsize_;
const int in_stride = (row_end - row_start) *
VP8LSubSampleSize(transform->xsize_, transform->bits_);
uint32_t* const src = out + out_stride - in_stride;
memmove(src, out, in_stride * sizeof(*src));
ColorIndexInverseTransform(transform, row_start, row_end, src, out);
} else {
ColorIndexInverseTransform(transform, row_start, row_end, in, out);
}
break;
}
}