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gif2webp: Background color correction

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For some GIF images, the first frame is missing the corresponding
graphic control extension. For such cases, we were never calling
GetBackgroundColor(), and default background color value (white) was being used
incorrectly.
So, we call GetBackgroundColor() when we encounter the first image
descriptor instead, to make sure that it is always called.

(cherry picked from commit 0cc811d7d6)

Change-Id: I00fc8e943d8a0c1578dcd718f3e74dec7de4ed61
This commit is contained in:
Urvang Joshi 2014-09-18 15:07:28 -07:00 committed by James Zern
parent f8b7d94daa
commit 8de0debcec
1 changed files with 10 additions and 12 deletions
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20
examples/gif2webp.c
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@ -174,21 +174,22 @@ static int ReadFrame(GifFileType* const gif, WebPFrameRect* const gif_rect,
return ok; return ok;
} }
static int GetBackgroundColor(const ColorMapObject* const color_map, static void GetBackgroundColor(const ColorMapObject* const color_map,
int bgcolor_idx, uint32_t* const bgcolor) { int bgcolor_idx, uint32_t* const bgcolor) {
if (transparent_index != -1 && bgcolor_idx == transparent_index) { if (transparent_index != -1 && bgcolor_idx == transparent_index) {
*bgcolor = WEBP_UTIL_TRANSPARENT_COLOR; // Special case. *bgcolor = WEBP_UTIL_TRANSPARENT_COLOR; // Special case.
return 1;
} else if (color_map == NULL || color_map->Colors == NULL } else if (color_map == NULL || color_map->Colors == NULL
|| bgcolor_idx >= color_map->ColorCount) { || bgcolor_idx >= color_map->ColorCount) {
return 0; // Invalid color map or index. *bgcolor = WHITE_COLOR;
fprintf(stderr,
"GIF decode warning: invalid background color index. Assuming "
"white background.\n");
} else { } else {
const GifColorType color = color_map->Colors[bgcolor_idx]; const GifColorType color = color_map->Colors[bgcolor_idx];
*bgcolor = (0xff << 24) *bgcolor = (0xff << 24)
| (color.Red << 16) | (color.Red << 16)
| (color.Green << 8) | (color.Green << 8)
| (color.Blue << 0); | (color.Blue << 0);
return 1;
} }
} }
@ -483,6 +484,10 @@ int main(int argc, const char *argv[]) {
cache = WebPFrameCacheNew(frame.width, frame.height, cache = WebPFrameCacheNew(frame.width, frame.height,
kmin, kmax, allow_mixed); kmin, kmax, allow_mixed);
if (cache == NULL) goto End; if (cache == NULL) goto End;
// Background color.
GetBackgroundColor(gif->SColorMap, gif->SBackGroundColor,
&anim.bgcolor);
} }
// Some even more broken GIF can have sub-rect with zero width/height. // Some even more broken GIF can have sub-rect with zero width/height.
if (image_desc->Width == 0 || image_desc->Height == 0) { if (image_desc->Width == 0 || image_desc->Height == 0) {
@ -544,13 +549,6 @@ int main(int argc, const char *argv[]) {
: WEBP_MUX_DISPOSE_NONE; : WEBP_MUX_DISPOSE_NONE;
} }
transparent_index = (flags & GIF_TRANSPARENT_MASK) ? data[4] : -1; transparent_index = (flags & GIF_TRANSPARENT_MASK) ? data[4] : -1;
if (is_first_frame) {
if (!GetBackgroundColor(gif->SColorMap, gif->SBackGroundColor,
&anim.bgcolor)) {
fprintf(stderr, "GIF decode warning: invalid background color "
"index. Assuming white background.\n");
}
}
break; break;
} }
case PLAINTEXT_EXT_FUNC_CODE: { case PLAINTEXT_EXT_FUNC_CODE: {