RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-25 06:57:44 +00:00
Code Issues Activity Actions

LibGfx: correctly handle transparency between GIF frames

Browse source 
This fixes an issue where transparent pixels in GIF animation frames
have their alpha values incorrectly set to zero, allowing the
background behind the GIF to show through, instead of the previous
animation frame.

Additionally, transparent pixels are now correctly identified based on
their index matching the image transparency index, instead of their
color values.
This commit is contained in:
Peter Nelson 2020-08-12 17:09:37 +01:00 • committed by Andreas Kling
parent 0ab37b44a1
commit daa762bb06
1 changed files with 6 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

16
Libraries/LibGfx/GIFLoader.cpp
View file

@ -292,11 +292,6 @@ static bool decode_frames_up_to_index(GIFLoadingContext& context, size_t frame_i
}
int pixel_index = 0;
RGB transparent_color { 0, 0, 0 };
if (image.transparent) {
transparent_color = context.logical_screen.color_map[image.transparency_index];
}
while (true) {
Optional<u16> code = decoder.next_code();
if (!code.has_value()) {
@ -321,13 +316,14 @@ static bool decode_frames_up_to_index(GIFLoadingContext& context, size_t frame_i
Color c = Color(rgb.r, rgb.g, rgb.b);
if (image.transparent) {
if (rgb.r == transparent_color.r && rgb.g == transparent_color.g && rgb.b == transparent_color.b) {
c.set_alpha(0);
}
if (image.transparent && color == image.transparency_index) {
c.set_alpha(0);
}
if (!image.transparent || image.disposal_method == ImageDescriptor::DisposalMethod::None || color != image.transparency_index) {
image.bitmap->set_pixel(x, y, c);
}
image.bitmap->set_pixel(x, y, c);
++pixel_index;
}
}