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add colorspace for premultiplied alpha

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The new modes are
       MODE_rgbA
       MODE_bgrA
       MODE_Argb
       MODE_rgbA_4444
It's binary incompatible, since the enums changed.

While at it, i removed the now unneeded KeepAlpha methods.
-> Saved ~12k of code!

* made explicit mention that alpha_plane is persistent,
so we have access to the full alpha plane data at all time.
Incremental decoding of alpha was planned for, but not
implemented. So better not dragged this constaint for now
and make the code easier until we revisit that.

Change-Id: Idaba281a6ca819965ca062d1c23329f36d90c7ff
This commit is contained in:
Pascal Massimino
2012-06-04 07:40:32 -07:00
parent 5f7bb3f53a
commit 48f827574e
13 changed files with 303 additions and 122 deletions
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132
src/dsp/upsampling.c
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@ -23,7 +23,6 @@ extern "C" {
// Fancy upsampling functions to convert YUV to RGB
WebPUpsampleLinePairFunc WebPUpsamplers[MODE_LAST];
WebPUpsampleLinePairFunc WebPUpsamplersKeepAlpha[MODE_LAST];
// Given samples laid out in a square as:
// [a b]
@ -100,11 +99,6 @@ UPSAMPLE_FUNC(UpsampleBgraLinePair, VP8YuvToBgra, 4)
UPSAMPLE_FUNC(UpsampleArgbLinePair, VP8YuvToArgb, 4)
UPSAMPLE_FUNC(UpsampleRgba4444LinePair, VP8YuvToRgba4444, 2)
UPSAMPLE_FUNC(UpsampleRgb565LinePair, VP8YuvToRgb565, 2)
// These variants don't erase the alpha value
UPSAMPLE_FUNC(UpsampleRgbaKeepAlphaLinePair, VP8YuvToRgb, 4)
UPSAMPLE_FUNC(UpsampleBgraKeepAlphaLinePair, VP8YuvToBgr, 4)
UPSAMPLE_FUNC(UpsampleArgbKeepAlphaLinePair, VP8YuvToArgbKeepA, 4)
UPSAMPLE_FUNC(UpsampleRgba4444KeepAlphaLinePair, VP8YuvToRgba4444KeepA, 2)
#undef LOAD_UV
#undef UPSAMPLE_FUNC
@ -145,11 +139,6 @@ SAMPLE_FUNC(SampleBgraLinePair, VP8YuvToBgra, 4)
SAMPLE_FUNC(SampleArgbLinePair, VP8YuvToArgb, 4)
SAMPLE_FUNC(SampleRgba4444LinePair, VP8YuvToRgba4444, 2)
SAMPLE_FUNC(SampleRgb565LinePair, VP8YuvToRgb565, 2)
// These variants don't erase the alpha value
SAMPLE_FUNC(SampleRgbaKeepAlphaLinePair, VP8YuvToRgb, 4)
SAMPLE_FUNC(SampleBgraKeepAlphaLinePair, VP8YuvToBgr, 4)
SAMPLE_FUNC(SampleArgbKeepAlphaLinePair, VP8YuvToArgbKeepA, 4)
SAMPLE_FUNC(SampleRgba4444KeepAlphaLinePair, VP8YuvToRgba4444KeepA, 2)
#undef SAMPLE_FUNC
@ -160,17 +149,11 @@ const WebPSampleLinePairFunc WebPSamplers[MODE_LAST] = {
SampleBgraLinePair, // MODE_BGRA
SampleArgbLinePair, // MODE_ARGB
SampleRgba4444LinePair, // MODE_RGBA_4444
SampleRgb565LinePair // MODE_RGB_565
};
const WebPSampleLinePairFunc WebPSamplersKeepAlpha[MODE_LAST] = {
SampleRgbLinePair, // MODE_RGB
SampleRgbaKeepAlphaLinePair, // MODE_RGBA
SampleBgrLinePair, // MODE_BGR
SampleBgraKeepAlphaLinePair, // MODE_BGRA
SampleArgbKeepAlphaLinePair, // MODE_ARGB
SampleRgba4444KeepAlphaLinePair, // MODE_RGBA_4444
SampleRgb565LinePair // MODE_RGB_565
SampleRgb565LinePair, // MODE_RGB_565
SampleRgbaLinePair, // MODE_rgbA
SampleBgraLinePair, // MODE_bgrA
SampleArgbLinePair, // MODE_Argb
SampleRgba4444LinePair // MODE_rgbA_4444
};
//------------------------------------------------------------------------------
@ -200,9 +183,82 @@ const WebPYUV444Converter WebPYUV444Converters[MODE_LAST] = {
Yuv444ToBgra, // MODE_BGRA
Yuv444ToArgb, // MODE_ARGB
Yuv444ToRgba4444, // MODE_RGBA_4444
Yuv444ToRgb565 // MODE_RGB_565
Yuv444ToRgb565, // MODE_RGB_565
Yuv444ToRgba, // MODE_rgbA
Yuv444ToBgra, // MODE_bgrA
Yuv444ToArgb, // MODE_Argb
Yuv444ToRgba4444 // MODE_rgbA_4444
};
//------------------------------------------------------------------------------
// Premultiplied modes
// non dithered-modes
// (x * a * 32897) >> 23 is bit-wise equivalent to (int)(x * a / 255.)
// for all 8bit x or a. For bit-wise equivalence to (int)(x * a / 255. + .5),
// one can use instead: (x * a * 65793 + (1 << 23)) >> 24
#if 1 // (int)(x * a / 255.)
#define MULTIPLIER(a) ((a) * 32897UL)
#define PREMULTIPLY(x, m) (((x) * (m)) >> 23)
#else // (int)(x * a / 255. + .5)
#define MULTIPLIER(a) ((a) * 65793UL)
#define PREMULTIPLY(x, m) (((x) * (m) + (1UL << 23)) >> 24)
#endif
static void ApplyAlphaMultiply(uint8_t* rgba, int alpha_1rst,
int w, int h, int stride) {
while (h-- > 0) {
uint8_t* const rgb = rgba + (alpha_1rst ? 1 : 0);
const uint8_t* const alpha = rgba + (alpha_1rst ? 0 : 3);
int i;
for (i = 0; i < w; ++i) {
const uint32_t a = alpha[4 * i];
if (a != 0xff) {
const uint32_t mult = MULTIPLIER(a);
rgb[4 * i + 0] = PREMULTIPLY(rgb[4 * i + 0], mult);
rgb[4 * i + 1] = PREMULTIPLY(rgb[4 * i + 1], mult);
rgb[4 * i + 2] = PREMULTIPLY(rgb[4 * i + 2], mult);
}
}
rgba += stride;
}
}
#undef MULTIPLIER
#undef PREMULTIPLY
// rgbA4444
#define MULTIPLIER(a) ((a) * 0x11)
#define PREMULTIPLY(x, m) (((x) * (m)) >> 12)
static WEBP_INLINE uint8_t dither_hi(uint8_t x) { return (x & 0xf0) | (x >> 4); }
static WEBP_INLINE uint8_t dither_lo(uint8_t x) { return (x & 0x0f) | (x << 4); }
static void ApplyAlphaMultiply4444(uint8_t* rgba4444,
int w, int h, int stride) {
while (h-- > 0) {
int i;
for (i = 0; i < w; ++i) {
const uint8_t a = dither_lo(rgba4444[2 * i + 1]);
const uint32_t mult = MULTIPLIER(a);
const uint8_t r = PREMULTIPLY(dither_hi(rgba4444[2 * i + 0]), mult);
const uint8_t g = PREMULTIPLY(dither_lo(rgba4444[2 * i + 0]), mult);
const uint8_t b = PREMULTIPLY(dither_hi(rgba4444[2 * i + 1]), mult);
rgba4444[2 * i + 0] = (r & 0xf0) | (g & 0x0f);
rgba4444[2 * i + 1] = (b & 0xf0) | a;
}
rgba4444 += stride;
}
}
#undef MULTIPLIER
#undef PREMULTIPLY
void (*WebPApplyAlphaMultiply)(uint8_t*, int, int, int, int)
= ApplyAlphaMultiply;
void (*WebPApplyAlphaMultiply4444)(uint8_t*, int, int, int)
= ApplyAlphaMultiply4444;
//------------------------------------------------------------------------------
// Main call
@ -216,16 +272,8 @@ void WebPInitUpsamplers(void) {
WebPUpsamplers[MODE_RGBA_4444] = UpsampleRgba4444LinePair;
WebPUpsamplers[MODE_RGB_565] = UpsampleRgb565LinePair;
WebPUpsamplersKeepAlpha[MODE_RGB] = UpsampleRgbLinePair;
WebPUpsamplersKeepAlpha[MODE_RGBA] = UpsampleRgbaKeepAlphaLinePair;
WebPUpsamplersKeepAlpha[MODE_BGR] = UpsampleBgrLinePair;
WebPUpsamplersKeepAlpha[MODE_BGRA] = UpsampleBgraKeepAlphaLinePair;
WebPUpsamplersKeepAlpha[MODE_ARGB] = UpsampleArgbKeepAlphaLinePair;
WebPUpsamplersKeepAlpha[MODE_RGBA_4444] = UpsampleRgba4444KeepAlphaLinePair;
WebPUpsamplersKeepAlpha[MODE_RGB_565] = UpsampleRgb565LinePair;
// If defined, use CPUInfo() to overwrite some pointers with faster versions.
if (VP8GetCPUInfo) {
if (VP8GetCPUInfo != NULL) {
#if defined(WEBP_USE_SSE2)
if (VP8GetCPUInfo(kSSE2)) {
WebPInitUpsamplersSSE2();
@ -235,6 +283,26 @@ void WebPInitUpsamplers(void) {
#endif // FANCY_UPSAMPLING
}
void WebPInitPremultiply(void) {
WebPApplyAlphaMultiply = ApplyAlphaMultiply;
WebPApplyAlphaMultiply4444 = ApplyAlphaMultiply4444;
#ifdef FANCY_UPSAMPLING
WebPUpsamplers[MODE_rgbA] = UpsampleRgbaLinePair;
WebPUpsamplers[MODE_bgrA] = UpsampleBgraLinePair;
WebPUpsamplers[MODE_Argb] = UpsampleArgbLinePair;
WebPUpsamplers[MODE_rgbA_4444] = UpsampleRgba4444LinePair;
if (VP8GetCPUInfo != NULL) {
#if defined(WEBP_USE_SSE2)
if (VP8GetCPUInfo(kSSE2)) {
WebPInitPremultiplySSE2();
}
#endif
}
#endif // FANCY_UPSAMPLING
}
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif