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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
View File

@ -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;
}

3
src/dec/alphai.h
View File

@ -28,13 +28,14 @@ struct ALPHDecoder {
int width_;
int height_;
int method_;
WEBP_FILTER_TYPE filter_;
WebPUnfilterFunc unfilter_func_;
int pre_processing_;
struct VP8LDecoder* vp8l_dec_;
VP8Io io_;
int use_8b_decode_; // Although alpha channel requires only 1 byte per
// pixel, sometimes VP8LDecoder may need to allocate
// 4 bytes per pixel internally during decode.
uint8_t* output_;
};
//------------------------------------------------------------------------------

40
src/dec/vp8l.c
View File

@ -717,15 +717,22 @@ static void ApplyInverseTransforms(VP8LDecoder* const dec, int num_rows,
// Special method for paletted alpha data.
static void ApplyInverseTransformsAlpha(VP8LDecoder* const dec, int num_rows,
const uint8_t* const rows) {
const ALPHDecoder* const alph_dec = (const ALPHDecoder*)dec->io_->opaque;
const int width = dec->io_->width;
uint8_t* const output = alph_dec->output_;
const int start_row = dec->last_row_;
const int end_row = start_row + num_rows;
const uint8_t* rows_in = rows;
uint8_t* rows_out = (uint8_t*)dec->io_->opaque + dec->io_->width * start_row;
uint8_t* rows_out = output + width * start_row;
VP8LTransform* const transform = &dec->transforms_[0];
assert(dec->next_transform_ == 1);
assert(transform->type_ == COLOR_INDEXING_TRANSFORM);
VP8LColorIndexInverseTransformAlpha(transform, start_row, end_row, rows_in,
rows_out);
if (alph_dec->unfilter_func_ != NULL) {
alph_dec->unfilter_func_(width, dec->io_->height, width,
start_row, num_rows, output);
}
}
// Processes (transforms, scales & color-converts) the rows decoded after the
@ -1453,38 +1460,39 @@ static void ExtractAlphaRows(VP8LDecoder* const dec, int row) {
assert(row <= dec->io_->crop_bottom);
if (num_rows > 0) {
// Extract alpha (which is stored in the green plane).
const ALPHDecoder* const alph_dec = (const ALPHDecoder*)dec->io_->opaque;
uint8_t* const output = alph_dec->output_;
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_;
uint8_t* const dst = output + 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;
if (alph_dec->unfilter_func_ != NULL) {
alph_dec->unfilter_func_(width, dec->io_->height, width,
dec->last_row_, num_rows, output);
}
}
dec->last_row_ = dec->last_out_row_ = row;
}
int VP8LDecodeAlphaHeader(ALPHDecoder* const alph_dec,
const uint8_t* const data, size_t data_size,
uint8_t* const output) {
const uint8_t* const data, size_t data_size) {
int ok = 0;
VP8LDecoder* dec;
VP8Io* io;
VP8LDecoder* dec = VP8LNew();
if (dec == NULL) return 0;
assert(alph_dec != NULL);
alph_dec->vp8l_dec_ = VP8LNew();
if (alph_dec->vp8l_dec_ == NULL) return 0;
dec = alph_dec->vp8l_dec_;
alph_dec->vp8l_dec_ = dec;
dec->width_ = alph_dec->width_;
dec->height_ = alph_dec->height_;
dec->io_ = &alph_dec->io_;
io = dec->io_;
VP8InitIo(io);
WebPInitCustomIo(NULL, io); // Just a sanity Init. io won't be used.
io->opaque = output;
io->width = alph_dec->width_;
io->height = alph_dec->height_;
dec->io_->opaque = alph_dec;
dec->io_->width = alph_dec->width_;
dec->io_->height = alph_dec->height_;
dec->status_ = VP8_STATUS_OK;
VP8LInitBitReader(&dec->br_, data, data_size);

3
src/dec/vp8li.h
View File

@ -100,8 +100,7 @@ struct ALPHDecoder; // Defined in dec/alphai.h.
// Decodes image header for alpha data stored using lossless compression.
// Returns false in case of error.
int VP8LDecodeAlphaHeader(struct ALPHDecoder* const alph_dec,
const uint8_t* const data, size_t data_size,
uint8_t* const output);
const uint8_t* const data, size_t data_size);
// Decodes *at least* 'last_row' rows of alpha. If some of the initial rows are
// already decoded in previous call(s), it will resume decoding from where it