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