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use header-less lossless bitstream for alpha channel

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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
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32
src/dec/alpha.c
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@ -11,7 +11,7 @@
#include <stdlib.h>
#include "./vp8i.h"
#include "../webp/decode.h"
#include "./vp8li.h"
#include "../utils/filters.h"
#include "../utils/quant_levels.h"
@ -79,26 +79,12 @@ static int DecodeAlpha(const uint8_t* data, size_t data_size,
ok = (data_size >= decoded_size);
decoded_data = (uint8_t*)data + ALPHA_HEADER_LEN;
} else {
size_t i;
int w, h;
uint32_t* const output =
(uint32_t*)WebPDecodeRGBA(data + ALPHA_HEADER_LEN,
data_size - ALPHA_HEADER_LEN,
&w, &h);
if (w != width || h != height || output == NULL) {
free(output);
return 0;
}
decoded_data = (uint8_t*)malloc(decoded_size);
if (decoded_data == NULL) {
free(output);
return 0;
}
for (i = 0; i < decoded_size; ++i) {
decoded_data[i] = (output[i] >> 8) & 0xff;
}
free(output);
ok = 1;
if (decoded_data == NULL) return 0;
ok = VP8LDecodeAlphaImageStream(width, height,
data + ALPHA_HEADER_LEN,
data_size - ALPHA_HEADER_LEN,
decoded_data);
}
if (ok) {
@ -119,9 +105,9 @@ static int DecodeAlpha(const uint8_t* data, size_t data_size,
// Construct raw_data (height x stride) from alpha data (height x width).
CopyPlane(decoded_data, width, output, stride, width, height);
}
}
if (pre_processing == ALPHA_PREPROCESSED_LEVELS) {
ok = DequantizeLevels(decoded_data, width, height);
if (pre_processing == ALPHA_PREPROCESSED_LEVELS) {
ok = DequantizeLevels(decoded_data, width, height);
}
}
Error: