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Change in lossless bit-stream.

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Change the lossless signature to 0x2f
Add 1 bit indicator for 'droppable (or trivial) alpha)'.
Add 3 bit lossless version (for future extension like yuv support).
Change the sub-resolution information to 3 bits implying range [2 .. 9]

Change-Id: Ic7b8c069240bbcd326cf5d5d4cd2dde8667851e2
This commit is contained in:
Vikas Arora
2012-06-04 12:46:01 +05:30
parent 5f7bb3f53a
commit 069f903a08
6 changed files with 64 additions and 26 deletions
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25
src/dec/vp8l.c
View File

@ -79,34 +79,37 @@ static int DecodeImageStream(int xsize, int ysize,
//------------------------------------------------------------------------------
int VP8LCheckSignature(const uint8_t* const data, size_t size) {
return (size >= 1) &&
(data[0] == VP8L_MAGIC_BYTE || data[0] == VP8L_MAGIC_BYTE_RSVD);
return (size >= 1) && (data[0] == VP8L_MAGIC_BYTE);
}
static int ReadImageSize(VP8LBitReader* const br,
int* const width, int* const height) {
static int ReadImageInfo(VP8LBitReader* const br,
int* const width, int* const height,
int* const has_alpha) {
const uint8_t signature = VP8LReadBits(br, 8);
if (!VP8LCheckSignature(&signature, 1)) {
return 0;
}
*width = VP8LReadBits(br, VP8L_IMAGE_SIZE_BITS) + 1;
*height = VP8LReadBits(br, VP8L_IMAGE_SIZE_BITS) + 1;
*has_alpha = VP8LReadBits(br, 1);
VP8LReadBits(br, VP8L_VERSION_BITS); // Read/ignore the version number.
return 1;
}
int VP8LGetInfo(const uint8_t* data, size_t data_size,
int* const width, int* const height) {
int* const width, int* const height, int* const has_alpha) {
if (data == NULL || data_size < kHeaderBytes) {
return 0; // not enough data
} else {
int w, h;
int w, h, a;
VP8LBitReader br;
VP8LInitBitReader(&br, data, data_size);
if (!ReadImageSize(&br, &w, &h)) {
if (!ReadImageInfo(&br, &w, &h, &a)) {
return 0;
}
if (width != NULL) *width = w;
if (height != NULL) *height = h;
if (has_alpha != NULL) *has_alpha = a;
return 1;
}
}
@ -308,7 +311,7 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize,
int num_htree_groups = 1;
if (VP8LReadBits(br, 1)) { // use meta Huffman codes
const int huffman_precision = VP8LReadBits(br, 4);
const int huffman_precision = VP8LReadBits(br, 3) + 2;
const int huffman_xsize = VP8LSubSampleSize(xsize, huffman_precision);
const int huffman_ysize = VP8LSubSampleSize(ysize, huffman_precision);
const int huffman_pixs = huffman_xsize * huffman_ysize;
@ -735,7 +738,7 @@ static int ReadTransform(int* const xsize, int const* ysize,
switch (type) {
case PREDICTOR_TRANSFORM:
case CROSS_COLOR_TRANSFORM:
transform->bits_ = VP8LReadBits(br, 4);
transform->bits_ = VP8LReadBits(br, 3) + 2;
ok = DecodeImageStream(VP8LSubSampleSize(transform->xsize_,
transform->bits_),
VP8LSubSampleSize(transform->ysize_,
@ -1006,7 +1009,7 @@ int VP8LDecodeAlphaImageStream(int width, int height, const uint8_t* const data,
//------------------------------------------------------------------------------
int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io) {
int width, height;
int width, height, has_alpha;
if (dec == NULL) return 0;
if (io == NULL) {
@ -1017,7 +1020,7 @@ int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io) {
dec->io_ = io;
dec->status_ = VP8_STATUS_OK;
VP8LInitBitReader(&dec->br_, io->data, io->data_size);
if (!ReadImageSize(&dec->br_, &width, &height)) {
if (!ReadImageInfo(&dec->br_, &width, &height, &has_alpha)) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
goto Error;
}

7
src/dec/vp8li.h
View File

@ -91,11 +91,10 @@ typedef struct {
int VP8LCheckSignature(const uint8_t* const data, size_t size);
// Validates the VP8L data-header and retrieves basic header information viz
// width and height. Returns 0 in case of formatting error. width/height
// can be passed NULL.
// width, height and alpha. Returns 0 in case of formatting error.
// width/height/has_alpha can be passed NULL.
int VP8LGetInfo(const uint8_t* data, size_t data_size, // data available so far
int* const width, int* const height);
int* const width, int* const height, int* const has_alpha);
// Decodes a raw image stream (without header) and store the alpha data
// into *output, which must be of size width x height. Returns false in case

5
src/dec/webp.c
View File

@ -577,11 +577,12 @@ static VP8StatusCode GetFeatures(const uint8_t* data, size_t data_size,
return VP8_STATUS_BITSTREAM_ERROR;
}
} else {
int has_alpha;
// Validates raw VP8L data.
if (!VP8LGetInfo(data, data_size, width, height)) {
if (!VP8LGetInfo(data, data_size, width, height, &has_alpha)) {
return VP8_STATUS_BITSTREAM_ERROR;
}
features->has_alpha = 1;
features->has_alpha = has_alpha;
}
return VP8_STATUS_OK; // Return features from VP8 header.