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lossless decoding: only process decoded row up to last_row

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there's some subtle changes:
  - DecodeAlphaData() may be called with pos==end because we don't want
    to decode more data (there's none left), but because we want to apply
    process_func() to all the unprocessed pixels already decoded
  - last_row is exclusive and should be understood as 'up to last_row'. Can be misleading.
  - VP8LDecodeAlphaImageStream() was testing dec->last_pixel_ for completion,
    which was wrong because last_pixel_ is the last *decoded* pixel, not the
    last *processed* one. -> test now uses last_row_, as expected

Change-Id: I1fb04ba25cd7a4775db9e3deee3e2ae80f9c0a75
This commit is contained in:
Pascal Massimino 2016-04-05 15:30:56 +02:00
parent 238cdcdbe1
commit a4cae68de0
1 changed files with 34 additions and 27 deletions
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61
src/dec/vp8l.c
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@ -734,14 +734,13 @@ static void ProcessRows(VP8LDecoder* const dec, int row) {
const uint32_t* const rows = dec->pixels_ + dec->width_ * dec->last_row_;
const int num_rows = row - dec->last_row_;
if (num_rows <= 0) return; // Nothing to be done.
ApplyInverseTransforms(dec, num_rows, rows);
// Emit output.
{
assert(row <= dec->io_->crop_bottom);
if (num_rows > 0) { // Emit output.
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);
if (!SetCropWindow(io, dec->last_row_, row, &rows_data, in_stride)) {
// Nothing to output (this time).
} else {
@ -787,9 +786,10 @@ static int Is8bOptimizable(const VP8LMetadata* const hdr) {
}
static void ExtractPalettedAlphaRows(VP8LDecoder* const dec, int row) {
const int num_rows = row - dec->last_row_;
const uint8_t* const in =
(uint8_t*)dec->pixels_ + dec->width_ * dec->last_row_;
const int num_rows = row - dec->last_row_;
assert(row <= dec->io_->crop_bottom);
if (num_rows > 0) {
ApplyInverseTransformsAlpha(dec, num_rows, in);
}
@ -922,14 +922,14 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
int col = dec->last_pixel_ % width;
VP8LBitReader* const br = &dec->br_;
VP8LMetadata* const hdr = &dec->hdr_;
const HTreeGroup* htree_group = GetHtreeGroupForPos(hdr, col, row);
int pos = dec->last_pixel_; // current position
const int end = width * height; // End of data
const int last = width * last_row; // Last pixel to decode
const int len_code_limit = NUM_LITERAL_CODES + NUM_LENGTH_CODES;
const int mask = hdr->huffman_mask_;
assert(htree_group != NULL);
assert(pos < end);
const HTreeGroup* htree_group =
(pos < last) ? GetHtreeGroupForPos(hdr, col, row) : NULL;
assert(pos <= end);
assert(last_row <= height);
assert(Is8bOptimizable(hdr));
@ -939,6 +939,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
if ((col & mask) == 0) {
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
assert(htree_group != NULL);
VP8LFillBitWindow(br);
code = ReadSymbol(htree_group->htrees[GREEN], br);
if (code < NUM_LITERAL_CODES) { // Literal
@ -948,7 +949,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
if (col >= width) {
col = 0;
++row;
if (row % NUM_ARGB_CACHE_ROWS == 0) {
if (row <= last_row && (row % NUM_ARGB_CACHE_ROWS == 0)) {
ExtractPalettedAlphaRows(dec, row);
}
}
@ -971,7 +972,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
while (col >= width) {
col -= width;
++row;
if (row % NUM_ARGB_CACHE_ROWS == 0) {
if (row <= last_row && (row % NUM_ARGB_CACHE_ROWS == 0)) {
ExtractPalettedAlphaRows(dec, row);
}
}
@ -985,7 +986,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
assert(br->eos_ == VP8LIsEndOfStream(br));
}
// Process the remaining rows corresponding to last row-block.
ExtractPalettedAlphaRows(dec, row);
ExtractPalettedAlphaRows(dec, row > last_row ? last_row : row);
End:
if (!ok || (br->eos_ && pos < end)) {
@ -1025,7 +1026,6 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
int col = dec->last_pixel_ % width;
VP8LBitReader* const br = &dec->br_;
VP8LMetadata* const hdr = &dec->hdr_;
HTreeGroup* htree_group = GetHtreeGroupForPos(hdr, col, row);
uint32_t* src = data + dec->last_pixel_;
uint32_t* last_cached = src;
uint32_t* const src_end = data + width * height; // End of data
@ -1036,7 +1036,8 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
VP8LColorCache* const color_cache =
(hdr->color_cache_size_ > 0) ? &hdr->color_cache_ : NULL;
const int mask = hdr->huffman_mask_;
assert(htree_group != NULL);
const HTreeGroup* htree_group =
(src < src_last) ? GetHtreeGroupForPos(hdr, col, row) : NULL;
assert(src < src_end);
assert(src_last <= src_end);
@ -1049,7 +1050,10 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
// Only update when changing tile. Note we could use this test:
// if "((((prev_col ^ col) | prev_row ^ row)) > mask)" -> tile changed
// but that's actually slower and needs storing the previous col/row.
if ((col & mask) == 0) htree_group = GetHtreeGroupForPos(hdr, col, row);
if ((col & mask) == 0) {
htree_group = GetHtreeGroupForPos(hdr, col, row);
}
assert(htree_group != NULL);
if (htree_group->is_trivial_code) {
*src = htree_group->literal_arb;
goto AdvanceByOne;
@ -1080,8 +1084,10 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
if (col >= width) {
col = 0;
++row;
if ((row % NUM_ARGB_CACHE_ROWS == 0) && (process_func != NULL)) {
process_func(dec, row);
if (process_func != NULL) {
if (row <= last_row && (row % NUM_ARGB_CACHE_ROWS == 0)) {
process_func(dec, row);
}
}
if (color_cache != NULL) {
while (last_cached < src) {
@ -1108,8 +1114,10 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
while (col >= width) {
col -= width;
++row;
if ((row % NUM_ARGB_CACHE_ROWS == 0) && (process_func != NULL)) {
process_func(dec, row);
if (process_func != NULL) {
if (row <= last_row && (row % NUM_ARGB_CACHE_ROWS == 0)) {
process_func(dec, row);
}
}
}
// Because of the check done above (before 'src' was incremented by
@ -1140,7 +1148,7 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
} else if (!br->eos_) {
// Process the remaining rows corresponding to last row-block.
if (process_func != NULL) {
process_func(dec, row);
process_func(dec, row > last_row ? last_row : row);
}
dec->status_ = VP8_STATUS_OK;
dec->last_pixel_ = (int)(src - data); // end-of-scan marker
@ -1442,16 +1450,15 @@ static void ExtractAlphaRows(VP8LDecoder* const dec, int row) {
const int num_rows = row - dec->last_row_;
const uint32_t* const in = dec->pixels_ + dec->width_ * dec->last_row_;
if (num_rows <= 0) return; // Nothing to be done.
ApplyInverseTransforms(dec, num_rows, in);
// Extract alpha (which is stored in the green plane).
{
assert(row <= dec->io_->crop_bottom);
if (num_rows > 0) {
// Extract alpha (which is stored in the green plane).
const int width = dec->io_->width; // the final width (!= dec->width_)
const int cache_pixs = width * num_rows;
uint8_t* const dst = (uint8_t*)dec->io_->opaque + width * dec->last_row_;
const uint32_t* const src = dec->argb_cache_;
int i;
ApplyInverseTransforms(dec, num_rows, in);
for (i = 0; i < cache_pixs; ++i) dst[i] = (src[i] >> 8) & 0xff;
}
dec->last_row_ = dec->last_out_row_ = row;
@ -1515,7 +1522,7 @@ int VP8LDecodeAlphaImageStream(ALPHDecoder* const alph_dec, int last_row) {
assert(dec != NULL);
assert(last_row <= dec->height_);
if (dec->last_pixel_ == dec->width_ * dec->height_) {
if (dec->last_row_ >= last_row) {
return 1; // done
}
@ -1611,7 +1618,7 @@ int VP8LDecodeImage(VP8LDecoder* const dec) {
// Decode.
if (!DecodeImageData(dec, dec->pixels_, dec->width_, dec->height_,
dec->height_, ProcessRows)) {
io->crop_bottom, ProcessRows)) {
goto Err;
}