auto merge of #5194 : hirschenberger/servo/gif_alpha_background, r=larsbergstrom

This is GIF specific. It's also done when the image is PNG but PNG is
handled separately with the PNG crate, whereas GIFs are handled by the
stb-image crate and the distinction between alpha and non-alpha-supporting
images was missing.
This commit is contained in:
bors-servo 2015-03-12 05:51:48 -06:00
commit 6593cf9ec4
6 changed files with 40 additions and 1 deletions

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@ -59,7 +59,12 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
match stb_image::load_from_memory_with_depth(buffer, FORCE_DEPTH, true) {
stb_image::LoadResult::ImageU8(mut image) => {
assert!(image.depth == 4);
byte_swap(image.data.as_mut_slice());
// handle gif separately because the alpha-channel has to be premultiplied
if is_gif(buffer) {
byte_swap_and_premultiply(image.data.as_mut_slice());
} else {
byte_swap(image.data.as_mut_slice());
}
Some(png::Image {
width: image.width as u32,
height: image.height as u32,
@ -77,3 +82,10 @@ pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
}
}
}
fn is_gif(buffer: &[u8]) -> bool {
match buffer {
[b'G',b'I',b'F',b'8', n, b'a', ..] if n == b'7' || n == b'9' => true,
_ => false
}
}

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@ -0,0 +1,13 @@
<!DOCTYPE html>
<html>
<head>
<title>Kaboom</title>
<style>
body {
background: #00ff00;
}
</style>
</head>
<body><img src=alpha_gif_a.gif></body>
</html>

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@ -0,0 +1,13 @@
<!DOCTYPE html>
<html>
<head>
<title>Kaboom</title>
<style>
body {
background: #00ff00;
}
</style>
</head>
<body><img src=alpha_gif_b.gif></body>
</html>

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@ -13,6 +13,7 @@ fragment=top != ../html/acid2.html acid2_ref.html
== acid1_a.html acid1_b.html
== acid2_noscroll.html acid2_ref_broken.html
== after_block_iteration.html after_block_iteration_ref.html
== alpha_gif_a.html alpha_gif_b.html
== alpha_png_a.html alpha_png_b.html
== anon_block_inherit_a.html anon_block_inherit_b.html
flaky_cpu == append_style_a.html append_style_b.html