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Fix the lossless specs a bit more.

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Bug: webp:551

Change-Id: I03f729f69d660f17e27cc601e91c703b241f1b83
This commit is contained in:
Vincent Rabaud 2022-07-25 22:34:54 +02:00
parent 7366f7f394
commit e91451b69b
1 changed files with 6 additions and 6 deletions
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12
doc/webp-lossless-bitstream-spec.txt
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@ -414,9 +414,9 @@ void ColorTransform(uint8 red, uint8 blue, uint8 green,
int tmp_blue = blue; int tmp_blue = blue;
// Applying the transform is just subtracting the transform deltas // Applying the transform is just subtracting the transform deltas
tmp_red -= ColorTransformDelta(p->green_to_red_, green); tmp_red -= ColorTransformDelta(trans->green_to_red_, green);
tmp_blue -= ColorTransformDelta(p->green_to_blue_, green); tmp_blue -= ColorTransformDelta(trans->green_to_blue_, green);
tmp_blue -= ColorTransformDelta(p->red_to_blue_, red); tmp_blue -= ColorTransformDelta(trans->red_to_blue_, red);
*new_red = tmp_red & 0xff; *new_red = tmp_red & 0xff;
*new_blue = tmp_blue & 0xff; *new_blue = tmp_blue & 0xff;
@ -470,7 +470,7 @@ channels.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
void InverseTransform(uint8 red, uint8 green, uint8 blue, void InverseTransform(uint8 red, uint8 green, uint8 blue,
ColorTransformElement *p, ColorTransformElement *trans,
uint8 *new_red, uint8 *new_blue) { uint8 *new_red, uint8 *new_blue) {
// Transformed values of red and blue components // Transformed values of red and blue components
int tmp_red = red; int tmp_red = red;
@ -769,13 +769,13 @@ distance code `3` indicates left-top pixel.
The decoder can convert a distance code `i` to a scan-line order distance The decoder can convert a distance code `i` to a scan-line order distance
`dist` as follows: `dist` as follows:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(xi, yi) = distance_map[i] (xi, yi) = distance_map[i]
dist = x + y * xsize dist = x + y * xsize
if (dist < 1) { if (dist < 1) {
dist = 1 dist = 1
} }
~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
where `distance_map` is the mapping noted above and `xsize` is the width of the where `distance_map` is the mapping noted above and `xsize` is the width of the
image in pixels. image in pixels.