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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/vp8.c
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@ -80,6 +80,13 @@ int VP8SetError(VP8Decoder* const dec,
int VP8GetInfo(const uint8_t* data, uint32_t data_size, uint32_t chunk_size,
int* width, int* height, int* has_alpha) {
// Alpha-data is stored outside VP8 data and is inferred from VP8X chunk.
// So, this function always returns *has_alpha = 0. This value should NOT
// be used.
if (has_alpha != NULL) {
*has_alpha = 0;
}
if (data_size < 10) {
return 0; // not enough data
}
@ -92,14 +99,6 @@ int VP8GetInfo(const uint8_t* data, uint32_t data_size, uint32_t chunk_size,
const int w = ((data[7] << 8) | data[6]) & 0x3fff;
const int h = ((data[9] << 8) | data[8]) & 0x3fff;
if (has_alpha) {
#ifdef WEBP_EXPERIMENTAL_FEATURES
if (data_size < 11) return 0;
*has_alpha = !!(data[10] & 0x80); // the colorspace_ bit
#else
*has_alpha = 0;
#endif
}
if (!key_frame) { // Not a keyframe.
return 0;
}
@ -269,7 +268,8 @@ int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
buf_size = io->data_size;
// Process Pre-VP8 chunks.
status = WebPParseHeaders(&buf, &buf_size, &vp8_chunk_size, &bytes_skipped);
status = WebPParseHeaders(&buf, &buf_size, &vp8_chunk_size, &bytes_skipped,
&dec->alpha_data_, &dec->alpha_data_size_);
if (status != VP8_STATUS_OK) {
return VP8SetError(dec, status, "Incorrect/incomplete header.");
}
@ -342,9 +342,6 @@ int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
"bad partition length");
}
dec->alpha_data_ = NULL;
dec->alpha_data_size_ = 0;
br = &dec->br_;
VP8InitBitReader(br, buf, buf + frm_hdr->partition_length_);
buf += frm_hdr->partition_length_;
@ -418,17 +415,9 @@ int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
if (frm_hdr->partition_length_ < kTrailerSize ||
ext_buf[kTrailerSize - 1] != kTrailerMarker) {
Error:
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"RIFF: Inconsistent extra information.");
}
// Alpha
size = (ext_buf[4] << 0) | (ext_buf[5] << 8) | (ext_buf[6] << 16);
if (frm_hdr->partition_length_ < size + kTrailerSize) {
goto Error;
}
dec->alpha_data_ = (size > 0) ? ext_buf - size : NULL;
dec->alpha_data_size_ = size;
// Layer
size = (ext_buf[0] << 0) | (ext_buf[1] << 8) | (ext_buf[2] << 16);