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perform alpha filtering within the decoding loop

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Change-Id: I221ae20ba879cd4f7b48d012db1bc5443d968e17
This commit is contained in:
Pascal Massimino
2016-04-05 10:58:20 -07:00
parent a4cae68de0
commit 774dfbdc34
4 changed files with 44 additions and 34 deletions
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32
src/dec/alpha.c
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@ -52,6 +52,7 @@ static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
const uint8_t* const alpha_data = data + ALPHA_HEADER_LEN;
const size_t alpha_data_size = data_size - ALPHA_HEADER_LEN;
int rsrv;
int filter;
VP8Io* const io = &dec->io_;
assert(data != NULL && output != NULL && src_io != NULL);
@ -65,30 +66,25 @@ static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
}
dec->method_ = (data[0] >> 0) & 0x03;
dec->filter_ = (data[0] >> 2) & 0x03;
filter = (data[0] >> 2) & 0x03;
dec->pre_processing_ = (data[0] >> 4) & 0x03;
rsrv = (data[0] >> 6) & 0x03;
if (dec->method_ < ALPHA_NO_COMPRESSION ||
dec->method_ > ALPHA_LOSSLESS_COMPRESSION ||
dec->filter_ >= WEBP_FILTER_LAST ||
filter >= WEBP_FILTER_LAST ||
dec->pre_processing_ > ALPHA_PREPROCESSED_LEVELS ||
rsrv != 0) {
return 0;
}
if (dec->method_ == ALPHA_NO_COMPRESSION) {
const size_t alpha_decoded_size = dec->width_ * dec->height_;
ok = (alpha_data_size >= alpha_decoded_size);
} else {
assert(dec->method_ == ALPHA_LOSSLESS_COMPRESSION);
ok = VP8LDecodeAlphaHeader(dec, alpha_data, alpha_data_size, output);
}
VP8FiltersInit();
dec->unfilter_func_ = WebPUnfilters[filter];
dec->output_ = output;
// Copy the necessary parameters from src_io to io
VP8InitIo(io);
WebPInitCustomIo(NULL, io);
io->opaque = output; // output plane
io->opaque = dec;
io->width = src_io->width;
io->height = src_io->height;
@ -99,6 +95,14 @@ static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
io->crop_bottom = src_io->crop_bottom;
// No need to copy the scaling parameters.
if (dec->method_ == ALPHA_NO_COMPRESSION) {
const size_t alpha_decoded_size = dec->width_ * dec->height_;
ok = (alpha_data_size >= alpha_decoded_size);
} else {
assert(dec->method_ == ALPHA_LOSSLESS_COMPRESSION);
ok = VP8LDecodeAlphaHeader(dec, alpha_data, alpha_data_size);
}
return ok;
}
@ -110,7 +114,6 @@ static int ALPHDecode(VP8Decoder* const dec, int row, int num_rows) {
ALPHDecoder* const alph_dec = dec->alph_dec_;
const int width = alph_dec->width_;
const int height = alph_dec->height_;
WebPUnfilterFunc unfilter_func = WebPUnfilters[alph_dec->filter_];
uint8_t* const output = dec->alpha_plane_;
if (alph_dec->method_ == ALPHA_NO_COMPRESSION) {
const size_t offset = row * width;
@ -118,6 +121,9 @@ static int ALPHDecode(VP8Decoder* const dec, int row, int num_rows) {
assert(dec->alpha_data_size_ >= ALPHA_HEADER_LEN + offset + num_pixels);
memcpy(dec->alpha_plane_ + offset,
dec->alpha_data_ + ALPHA_HEADER_LEN + offset, num_pixels);
if (alph_dec->unfilter_func_ != NULL) {
alph_dec->unfilter_func_(width, height, width, row, num_rows, output);
}
} else { // alph_dec->method_ == ALPHA_LOSSLESS_COMPRESSION
assert(alph_dec->vp8l_dec_ != NULL);
if (!VP8LDecodeAlphaImageStream(alph_dec, row + num_rows)) {
@ -125,10 +131,6 @@ static int ALPHDecode(VP8Decoder* const dec, int row, int num_rows) {
}
}
if (unfilter_func != NULL) {
unfilter_func(width, height, width, row, num_rows, output);
}
if (row + num_rows >= alph_dec->io_.crop_bottom) {
dec->is_alpha_decoded_ = 1;
}