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Add Alpha Decode support from WebPDecode.

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Extend WebP decode functionality to extract Alpha data (support ALPH
chunk) and decode the Alpha plane using Alpha (utils/alpha) core-lib.

Change-Id: I6f0ee1b189c13caba3c1dd9b681383bfd00aa212
This commit is contained in:
Vikas Arora
2011-12-01 08:57:36 +05:30
parent e1947a9299
commit d117a94046
8 changed files with 62 additions and 77 deletions
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29
src/dec/webp.c
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@ -12,6 +12,7 @@
#include <stdlib.h>
#include "vp8i.h"
#include "webpi.h"
#include "../webp/mux.h" // For 'ALPHA_FLAG'.
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
@ -105,17 +106,23 @@ VP8StatusCode WebPParseVP8X(const uint8_t** data, uint32_t* data_size,
VP8StatusCode WebPParseOptionalChunks(const uint8_t** data, uint32_t* data_size,
uint32_t riff_size,
uint32_t* bytes_skipped) {
uint32_t* bytes_skipped,
const uint8_t** alpha_data,
uint32_t* alpha_size) {
const uint8_t* buf;
uint32_t buf_size;
assert(data);
assert(data_size);
assert(bytes_skipped);
assert(alpha_data);
assert(alpha_size);
buf = *data;
buf_size = *data_size;
*bytes_skipped = 0;
*alpha_data = NULL;
*alpha_size = 0;
while (1) {
uint32_t chunk_size;
@ -145,7 +152,10 @@ VP8StatusCode WebPParseOptionalChunks(const uint8_t** data, uint32_t* data_size,
return VP8_STATUS_NOT_ENOUGH_DATA;
}
if (!memcmp(buf, "VP8 ", TAG_SIZE)) { // A valid VP8 header.
if (!memcmp(buf, "ALPH", TAG_SIZE)) { // A valid ALPH header.
*alpha_data = buf + CHUNK_HEADER_SIZE;
*alpha_size = chunk_size;
} else if (!memcmp(buf, "VP8 ", TAG_SIZE)) { // A valid VP8 header.
return VP8_STATUS_OK; // Found.
}
@ -186,7 +196,9 @@ VP8StatusCode WebPParseVP8Header(const uint8_t** data, uint32_t* data_size,
}
VP8StatusCode WebPParseHeaders(const uint8_t** data, uint32_t* data_size,
uint32_t* vp8_size, uint32_t* bytes_skipped) {
uint32_t* vp8_size, uint32_t* bytes_skipped,
const uint8_t** alpha_data,
uint32_t* alpha_size) {
const uint8_t* buf;
uint32_t buf_size;
uint32_t riff_size;
@ -200,12 +212,16 @@ VP8StatusCode WebPParseHeaders(const uint8_t** data, uint32_t* data_size,
assert(data_size);
assert(vp8_size);
assert(bytes_skipped);
assert(alpha_data);
assert(alpha_size);
buf = *data;
buf_size = *data_size;
*vp8_size = 0;
*bytes_skipped = 0;
*alpha_data = NULL;
*alpha_size = 0;
if (buf == NULL || buf_size < RIFF_HEADER_SIZE) {
return VP8_STATUS_NOT_ENOUGH_DATA;
@ -224,7 +240,8 @@ VP8StatusCode WebPParseHeaders(const uint8_t** data, uint32_t* data_size,
if (vp8x_skip_size > 0) {
// Skip over optional chunks.
status = WebPParseOptionalChunks(&buf, &buf_size, riff_size,
&optional_data_size);
&optional_data_size,
alpha_data, alpha_size);
if (status != VP8_STATUS_OK) {
return status; // Found an invalid chunk size / Insufficient data.
}
@ -487,11 +504,11 @@ static VP8StatusCode GetFeatures(const uint8_t* data, uint32_t data_size,
&features->height, &flags);
if (status != VP8_STATUS_OK) {
return status; // Wrong VP8X / insufficient data.
}
if (vp8x_skip_size > 0) {
return VP8_STATUS_OK; // Return features from VP8X header.
}
features->has_alpha = !!(flags & ALPHA_FLAG);
// Skip over VP8 header.
status = WebPParseVP8Header(&data, &data_size, riff_size, &vp8_skip_size,
@ -505,7 +522,7 @@ static VP8StatusCode GetFeatures(const uint8_t* data, uint32_t data_size,
// Validates raw VP8 data.
if (!VP8GetInfo(data, data_size, vp8_chunk_size,
&features->width, &features->height, &features->has_alpha)) {
&features->width, &features->height, NULL)) {
return VP8_STATUS_BITSTREAM_ERROR;
}