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Add smart RGB->YUV conversion option -pre 4

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New function: WebPPictureSmartARGBToYUVA()
This implement smart RGB->YUV conversion.

This is rather undocumented for now, and is triggered using '-pre 4'
preprocessing option.

This is slow-ish and use quite some memory, but should be improvable.
This is somehow a usable beta version.

Change-Id: Ia50a8c30134e4cab8a7d3eb70aef13ce1f6187a1
This commit is contained in:
skal
2014-08-15 10:55:09 -07:00
parent 137e609016
commit 3fc4c539aa
4 changed files with 548 additions and 99 deletions
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12
src/webp/encode.h
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@ -441,13 +441,14 @@ WEBP_EXTERN(int) WebPPictureImportBGRA(
WEBP_EXTERN(int) WebPPictureImportBGRX(
WebPPicture* picture, const uint8_t* bgrx, int bgrx_stride);
// Converts picture->argb data to the YUVA format specified by 'colorspace'.
// Converts picture->argb data to the YUV420A format. The 'colorspace'
// parameter is deprecated and should be equal to WEBP_YUV420.
// Upon return, picture->use_argb is set to false. The presence of real
// non-opaque transparent values is detected, and 'colorspace' will be
// adjusted accordingly. Note that this method is lossy.
// Returns false in case of error.
WEBP_EXTERN(int) WebPPictureARGBToYUVA(WebPPicture* picture,
WebPEncCSP colorspace);
WebPEncCSP /*colorspace = WEBP_YUV420*/);
// Same as WebPPictureARGBToYUVA(), but the conversion is done using
// pseudo-random dithering with a strength 'dithering' between
@ -456,6 +457,13 @@ WEBP_EXTERN(int) WebPPictureARGBToYUVA(WebPPicture* picture,
WEBP_EXTERN(int) WebPPictureARGBToYUVADithered(
WebPPicture* picture, WebPEncCSP colorspace, float dithering);
// Performs 'smart' RGBA->YUVA420 downsampling and colorspace conversion.
// Downsampling is handled with extra care in case of color clipping. This
// method is roughly 2x slower than WebPPictureARGBToYUVA() but produces better
// YUV representation.
// Returns false in case of error.
WEBP_EXTERN(int) WebPPictureSmartARGBToYUVA(WebPPicture* picture);
// Converts picture->yuv to picture->argb and sets picture->use_argb to true.
// The input format must be YUV_420 or YUV_420A.
// Note that the use of this method is discouraged if one has access to the