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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
transforming a green-only image, using the green value as an index
to this one-dimensional array.
5. Color transformation image. Defines signed 3.5 fixed-point
multipliers that are used to predict the red, green, and blue
components, to reduce entropy.
5. Color transform image. It is created by `ColorTransformElement` values
(defined in [Color Transform](#color-transform)) for different blocks of
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
into a set of fixed-size blocks (typically 16x16 blocks). Each of these