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Lossless bitstream clarification:

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Clarify what the pixels of a color transform image are.

Change-Id: I720248b5417857468d54952440cf1bae6c091042
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Urvang Joshi 2012-12-12 14:03:44 -08:00
parent 6bf208748c
commit bcec339b01
1 changed files with 5 additions and 3 deletions
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doc/webp-lossless-bitstream-spec.txt
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@ -604,9 +604,11 @@ to entropy coding, and three further roles related to transforms.
4. Color indexing image. An array of up to 256 ARGB colors is used for 4. Color indexing image. An array of up to 256 ARGB colors is used for
transforming a green-only image, using the green value as an index transforming a green-only image, using the green value as an index
to this one-dimensional array. to this one-dimensional array.
5. Color transformation image. Defines signed 3.5 fixed-point 5. Color transform image. It is created by `ColorTransformElement` values
multipliers that are used to predict the red, green, and blue (defined in [Color Transform](#color-transform)) for different blocks of
components, to reduce entropy. the image. Each `ColorTransformElement` `'cte'` is treated as a pixel whose
alpha component is `255`, red component is `cte.red_to_blue`, green
component is `cte.green_to_blue` and blue component is `cte.green_to_red`.
To divide the image into multiple regions, the image is first divided To divide the image into multiple regions, the image is first divided
into a set of fixed-size blocks (typically 16x16 blocks). Each of these into a set of fixed-size blocks (typically 16x16 blocks). Each of these