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Demux: WebPIterator now also denotes if the frame has alpha.

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Change-Id: Ia300385a49c1ee5afa8f114f2560ee8d1c7664bb
This commit is contained in:
Urvang Joshi 2013-07-18 19:41:38 -07:00
parent 6df743a33e
commit a03c3516cb
3 changed files with 15 additions and 16 deletions
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2
NEWS
View File

@ -4,6 +4,8 @@
* Significant memory reduction for decoding lossy images with alpha.
* Intertwined decoding of RGB and alpha for a shorter
time-to-first-decoded-pixel.
* WebPIterator has a new member 'has_alpha' denoting whether the frame
contains transparency.
- 6/13/13: version 0.3.1
This is a binary compatible release.

24
src/demux/demux.c
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@ -47,6 +47,7 @@ typedef struct {
typedef struct Frame {
int x_offset_, y_offset_;
int width_, height_;
int has_alpha_;
int duration_;
WebPMuxAnimDispose dispose_method_;
int is_fragment_; // this is a frame fragment (and not a full frame).
@ -196,18 +197,13 @@ static int AddFrame(WebPDemuxer* const dmux, Frame* const frame) {
}
// Store image bearing chunks to 'frame'.
// If 'has_vp8l_alpha' is not NULL, it will be set to true if the frame is a
// lossless image with alpha.
static ParseStatus StoreFrame(int frame_num, uint32_t min_size,
MemBuffer* const mem, Frame* const frame,
int* const has_vp8l_alpha) {
MemBuffer* const mem, Frame* const frame) {
int alpha_chunks = 0;
int image_chunks = 0;
int done = (MemDataSize(mem) < min_size);
ParseStatus status = PARSE_OK;
if (has_vp8l_alpha != NULL) *has_vp8l_alpha = 0; // Default.
if (done) return PARSE_NEED_MORE_DATA;
do {
@ -229,6 +225,7 @@ static ParseStatus StoreFrame(int frame_num, uint32_t min_size,
++alpha_chunks;
frame->img_components_[1].offset_ = chunk_start_offset;
frame->img_components_[1].size_ = chunk_size;
frame->has_alpha_ = 1;
frame->frame_num_ = frame_num;
Skip(mem, payload_available);
} else {
@ -258,7 +255,7 @@ static ParseStatus StoreFrame(int frame_num, uint32_t min_size,
frame->img_components_[0].size_ = chunk_size;
frame->width_ = features.width;
frame->height_ = features.height;
if (has_vp8l_alpha != NULL) *has_vp8l_alpha = features.has_alpha;
frame->has_alpha_ |= features.has_alpha;
frame->frame_num_ = frame_num;
frame->complete_ = (status == PARSE_OK);
Skip(mem, payload_available);
@ -325,8 +322,7 @@ static ParseStatus ParseAnimationFrame(
// Store a frame only if the animation flag is set there is some data for
// this frame is available.
status = StoreFrame(dmux->num_frames_ + 1, anmf_payload_size, mem, frame,
NULL);
status = StoreFrame(dmux->num_frames_ + 1, anmf_payload_size, mem, frame);
if (status != PARSE_ERROR && has_frames && frame->frame_num_ > 0) {
added_frame = AddFrame(dmux, frame);
if (added_frame) {
@ -361,7 +357,7 @@ static ParseStatus ParseFragment(WebPDemuxer* const dmux,
// Store a fragment only if the fragments flag is set there is some data for
// this fragment is available.
status = StoreFrame(frame_num, frgm_payload_size, mem, frame, NULL);
status = StoreFrame(frame_num, frgm_payload_size, mem, frame);
if (status != PARSE_ERROR && has_fragments && frame->frame_num_ > 0) {
added_fragment = AddFrame(dmux, frame);
if (!added_fragment) {
@ -424,7 +420,6 @@ static ParseStatus ParseSingleImage(WebPDemuxer* const dmux) {
MemBuffer* const mem = &dmux->mem_;
Frame* frame;
ParseStatus status;
int has_vp8l_alpha = 0; // Frame contains a lossless image with alpha.
if (dmux->frames_ != NULL) return PARSE_ERROR;
if (SizeIsInvalid(mem, min_size)) return PARSE_ERROR;
@ -435,14 +430,14 @@ static ParseStatus ParseSingleImage(WebPDemuxer* const dmux) {
// For the single image case we allow parsing of a partial frame, but we need
// at least CHUNK_HEADER_SIZE for parsing.
status = StoreFrame(1, CHUNK_HEADER_SIZE, &dmux->mem_, frame,
&has_vp8l_alpha);
status = StoreFrame(1, CHUNK_HEADER_SIZE, &dmux->mem_, frame);
if (status != PARSE_ERROR) {
const int has_alpha = !!(dmux->feature_flags_ & ALPHA_FLAG);
// Clear any alpha when the alpha flag is missing.
if (!has_alpha && frame->img_components_[1].size_ > 0) {
frame->img_components_[1].offset_ = 0;
frame->img_components_[1].size_ = 0;
frame->has_alpha_ = 0;
}
// Use the frame width/height as the canvas values for non-vp8x files.
@ -451,7 +446,7 @@ static ParseStatus ParseSingleImage(WebPDemuxer* const dmux) {
dmux->state_ = WEBP_DEMUX_PARSED_HEADER;
dmux->canvas_width_ = frame->width_;
dmux->canvas_height_ = frame->height_;
dmux->feature_flags_ |= has_vp8l_alpha ? ALPHA_FLAG : 0;
dmux->feature_flags_ |= frame->has_alpha_ ? ALPHA_FLAG : 0;
}
AddFrame(dmux, frame);
dmux->num_frames_ = 1;
@ -836,6 +831,7 @@ static int SynthesizeFrame(const WebPDemuxer* const dmux,
iter->y_offset = fragment->y_offset_;
iter->width = fragment->width_;
iter->height = fragment->height_;
iter->has_alpha = fragment->has_alpha_;
iter->duration = fragment->duration_;
iter->dispose_method = fragment->dispose_method_;
iter->complete = fragment->complete_;

5
src/webp/demux.h
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@ -53,7 +53,7 @@
extern "C" {
#endif
#define WEBP_DEMUX_ABI_VERSION 0x0100 // MAJOR(8b) + MINOR(8b)
#define WEBP_DEMUX_ABI_VERSION 0x0101 // MAJOR(8b) + MINOR(8b)
// Note: forward declaring enumerations is not allowed in (strict) C and C++,
// the types are left here for reference.
@ -136,8 +136,9 @@ struct WebPIterator {
// may still be decoded with the WebP incremental decoder.
WebPData fragment; // The frame or fragment given by 'frame_num' and
// 'fragment_num'.
int has_alpha; // True if the frame or fragment contains transparency.
uint32_t pad[4]; // padding for later use.
uint32_t pad[3]; // padding for later use.
void* private_; // for internal use only.
};