dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2025-07-15 21:39:59 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

use header-less lossless bitstream for alpha channel

Browse Source 
This saves ~26 bytes of headers.
* introduce new VP8LDecodeAlphaImageStream() for decoding
* use VP8LEncodeStream() for encoding
* refactor code a bit

still TODO: make the alpha-quality/enc-method user-configurable

Change-Id: I23e599bebe335cfb5868e746e076c3358ef12e71
This commit is contained in:
Pascal Massimino
2012-05-23 08:01:44 -07:00
parent 75d7f3b222
commit 39bf5d6497
4 changed files with 118 additions and 64 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
src/enc/alpha.c
View File

@ -28,8 +28,8 @@ extern "C" {
// -----------------------------------------------------------------------------
// int EncodeAlpha(const uint8_t* data, int width, int height, int stride,
// int quality, int method, int filter,
// uint8_t** output, size_t* output_size)
// int quality, int method, int filter,
// uint8_t** output, size_t* output_size)
//
// Encodes the given alpha data 'data' of size 'stride'x'height' via specified
// compression method 'method'. The pre-processing (Quantization) is
@ -54,16 +54,6 @@ extern "C" {
#ifdef USE_LOSSLESS_ENCODER
#include "../enc/vp8li.h"
#include "../webp/encode.h"
static int MyWriter(const uint8_t* data, size_t data_size,
const WebPPicture* const picture) {
VP8BitWriter* const bw = (VP8BitWriter*)picture->custom_ptr;
if (data_size > 0) {
VP8BitWriterAppend(bw, data, data_size);
}
return !bw->error_;
}
static int EncodeLossless(const uint8_t* data, int width, int height,
VP8BitWriter* const bw) {
@ -71,6 +61,7 @@ static int EncodeLossless(const uint8_t* data, int width, int height,
int ok = 0;
WebPConfig config;
WebPPicture picture;
VP8LBitWriter tmp_bw;
WebPPictureInit(&picture);
picture.width = width;
@ -78,6 +69,7 @@ static int EncodeLossless(const uint8_t* data, int width, int height,
picture.use_argb_input = 1;
if (!WebPPictureAlloc(&picture)) return 0;
// Transfer the alpha values to the green channel.
{
int i, j;
uint32_t* dst = picture.argb;
@ -90,16 +82,21 @@ static int EncodeLossless(const uint8_t* data, int width, int height,
dst += picture.argb_stride;
}
}
picture.writer = MyWriter;
picture.custom_ptr = (void*)bw;
WebPConfigInit(&config);
config.lossless = 1;
config.method = 2;
config.quality = 100;
config.quality = 100; // TODO(skal): make it adjustable.
ok = WebPEncode(&config, &picture);
VP8LBitWriterInit(&tmp_bw, (width * height) >> 3);
ok = (VP8LEncodeStream(&config, &picture, &tmp_bw) == VP8_ENC_OK);
WebPPictureFree(&picture);
if (ok) {
const uint8_t* const data = VP8LBitWriterFinish(&tmp_bw);
const size_t data_size = VP8LBitWriterNumBytes(&tmp_bw);
VP8BitWriterAppend(bw, data, data_size);
}
VP8LBitWriterDestroy(&tmp_bw);
return ok && !bw->error_;
}
@ -107,7 +104,7 @@ static int EncodeLossless(const uint8_t* data, int width, int height,
// -----------------------------------------------------------------------------
static int EncodeAlphaInternal(const uint8_t* data, int width, int height,
static int EncodeAlphaInternal(const uint8_t* data, int width, int height,
int method, int filter, int reduce_levels,
uint8_t* tmp_alpha, VP8BitWriter* const bw) {
int ok = 0;