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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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4
src/dec/webp.c
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@ -477,7 +477,7 @@ static uint8_t* Decode(WEBP_CSP_MODE mode, const uint8_t* data,
WebPCopyDecBuffer(&output, keep_info);
}
// return decoded samples (don't clear 'output'!)
return (mode >= MODE_YUV) ? output.u.YUVA.y : output.u.RGBA.rgba;
return WebPIsRGBMode(mode) ? output.u.RGBA.rgba : output.u.YUVA.y;
}
uint8_t* WebPDecodeRGB(const uint8_t* data, size_t data_size,
@ -684,7 +684,7 @@ int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
h = options->crop_height;
x = options->crop_left;
y = options->crop_top;
if (src_colorspace >= MODE_YUV) { // only snap for YUV420 or YUV422
if (!WebPIsRGBMode(src_colorspace)) { // only snap for YUV420 or YUV422
x &= ~1;
y &= ~1; // TODO(later): only for YUV420, not YUV422.
}