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webp-lossless-bitstream-spec: add amendment note
for fixes to the distance_map pseudo-code, the inverse color transform description and the num_code_lengths check. Bug: webp:448 Bug: webp:551 Change-Id: Id7e791b97704dd64bb9519657ce48b92cb457ae4
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@ -18,6 +18,8 @@ Paragraphs marked as \[AMENDED\] were amended on 2014-09-16.
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Paragraphs marked as \[AMENDED2\] were amended on 2022-05-13.
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Paragraphs marked as \[AMENDED3\] were amended on 2022-11-21.
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Abstract
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--------
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@ -465,7 +467,7 @@ During decoding, `ColorTransformElement` instances of the blocks are
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decoded and the inverse color transform is applied on the ARGB values of
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the pixels. As mentioned earlier, that inverse color transform is just
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adding `ColorTransformElement` values to the red and blue
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channels.
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channels. \[AMENDED3\]
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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void InverseTransform(uint8 red, uint8 green, uint8 blue,
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@ -771,6 +773,8 @@ Similarly, the distance code `3` indicates the left-top pixel.
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The decoder can convert a distance code `i` to a scan-line order distance
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`dist` as follows:
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\[AMENDED3\]
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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(xi, yi) = distance_map[i - 1]
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dist = xi + yi * xsize
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@ -910,7 +914,7 @@ First, `num_code_lengths` specifies the number of code lengths.
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int num_code_lengths = 4 + ReadBits(4);
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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If `num_code_lengths` is > 19, the bitstream is invalid.
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If `num_code_lengths` is > 19, the bitstream is invalid. \[AMENDED3\]
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The code lengths are themselves encoded using prefix codes: lower level code
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lengths, `code_length_code_lengths`, first have to be read. The rest of those
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