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bugfix: last alpha rows were incorrectly decoded

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sometimes, the last rows of the alpha plane contain more than NUM_ARGB_CACHE_ROWS
rows to process. But ExtractAlphaRows() was repeatedly calling ApplyInverseTransforms()
without updating the dec->last_row_ field, which is the starting row used as starting
point.

Fix would consist of either updating correctly dec->last_row_ before calling
ApplyInverseTransforms(). Or pass the starting row explicitly, which is simpler.

BUG=webp:439

Change-Id: Id99f2c28662d02b2b866cb79e666050be9d59e04
This commit is contained in:
Skal 2019-08-30 14:13:28 +02:00
parent 24d2ccb4e0
commit 0e48d889eb
1 changed files with 5 additions and 5 deletions
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10
src/dec/vp8l_dec.c
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@ -754,11 +754,11 @@ static WEBP_INLINE HTreeGroup* GetHtreeGroupForPos(VP8LMetadata* const hdr,
typedef void (*ProcessRowsFunc)(VP8LDecoder* const dec, int row);
static void ApplyInverseTransforms(VP8LDecoder* const dec, int num_rows,
static void ApplyInverseTransforms(VP8LDecoder* const dec,
int start_row, int num_rows,
const uint32_t* const rows) {
int n = dec->next_transform_;
const int cache_pixs = dec->width_ * num_rows;
const int start_row = dec->last_row_;
const int end_row = start_row + num_rows;
const uint32_t* rows_in = rows;
uint32_t* const rows_out = dec->argb_cache_;
@ -789,8 +789,7 @@ static void ProcessRows(VP8LDecoder* const dec, int row) {
VP8Io* const io = dec->io_;
uint8_t* rows_data = (uint8_t*)dec->argb_cache_;
const int in_stride = io->width * sizeof(uint32_t); // in unit of RGBA
ApplyInverseTransforms(dec, num_rows, rows);
ApplyInverseTransforms(dec, dec->last_row_, num_rows, rows);
if (!SetCropWindow(io, dec->last_row_, row, &rows_data, in_stride)) {
// Nothing to output (this time).
} else {
@ -1193,6 +1192,7 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
VP8LFillBitWindow(br);
dist_code = GetCopyDistance(dist_symbol, br);
dist = PlaneCodeToDistance(width, dist_code);
if (VP8LIsEndOfStream(br)) break;
if (src - data < (ptrdiff_t)dist || src_end - src < (ptrdiff_t)length) {
goto Error;
@ -1553,7 +1553,7 @@ static void ExtractAlphaRows(VP8LDecoder* const dec, int last_row) {
const int cache_pixs = width * num_rows_to_process;
uint8_t* const dst = output + width * cur_row;
const uint32_t* const src = dec->argb_cache_;
ApplyInverseTransforms(dec, num_rows_to_process, in);
ApplyInverseTransforms(dec, cur_row, num_rows_to_process, in);
WebPExtractGreen(src, dst, cache_pixs);
AlphaApplyFilter(alph_dec,
cur_row, cur_row + num_rows_to_process, dst, width);