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Bug 1801397. Render questionable 1x1 gifs with no image data like other clients. r=aosmond

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Differential Revision: https://phabricator.services.mozilla.com/D162450
This commit is contained in:
Timothy Nikkel
2022-12-15 00:41:56 +00:00
parent f69cf52d62
commit 5eb2686c15
6 changed files with 44 additions and 2 deletions
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16
image/decoders/nsGIFDecoder2.cpp
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@@ -150,6 +150,22 @@ bool nsGIFDecoder2::CheckForTransparency(const OrientedIntRect& aFrameRect) {
return true; return true;
} }
// This is a bit of a hack. Some sites will use a 1x1 gif that includes no
// header information indicating it is transparent, no palette, and no image
// data at all (so no pixels get written) to represent a transparent pixel
// using the absolute least number of bytes. Generally things are setup to
// detect transparency without decoding the image data. So to detect this kind
// of transparency without decoing the image data we would have to assume
// every gif is transparent, which we would like to avoid. Changing things so
// that we can detect transparency at any point of decoding is a bigger change
// and not worth it for one questionable 1x1 gif. Using this "trick" for
// anything but 1x1 transparent spacer gifs doesn't make sense, so it's
// reasonable to target 1x1 gifs just for this.
if (mGIFStruct.screen_width == 1 && mGIFStruct.screen_height == 1) {
PostHasTransparency();
return true;
}
if (mGIFStruct.images_decoded > 0) { if (mGIFStruct.images_decoded > 0) {
return false; // We only care about first frame padding below. return false; // We only care about first frame padding below.
} }

3
image/test/gtest/Common.cpp
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@@ -923,7 +923,8 @@ ImageTestCase DownscaledTransparentICOWithANDMaskTestCase() {
} }
ImageTestCase TruncatedSmallGIFTestCase() { ImageTestCase TruncatedSmallGIFTestCase() {
return ImageTestCase("green-1x1-truncated.gif", "image/gif", IntSize(1, 1)); return ImageTestCase("green-1x1-truncated.gif", "image/gif", IntSize(1, 1),
TEST_CASE_IS_TRANSPARENT);
} }
ImageTestCase LargeICOWithBMPTestCase() { ImageTestCase LargeICOWithBMPTestCase() {

2
image/test/mochitest/test_has_transparency.html
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@@ -43,7 +43,7 @@ function* testFiles() {
// PNGs and GIFs may be transparent or not. // PNGs and GIFs may be transparent or not.
yield ["red.png", false]; yield ["red.png", false];
yield ["transparent.png", true]; yield ["transparent.png", true];
yield ["red.gif", false]; yield ["animated-gif-finalframe.gif", false];
yield ["transparent.gif", true]; yield ["transparent.gif", true];
// GIFs with padding on the first frame are always transparent. // GIFs with padding on the first frame are always transparent.

11
image/test/reftest/gif/one-pixel-no-image-data-ref.html Normal file
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@@ -0,0 +1,11 @@
<!DOCTYPE html>
<style>
html{
background-color:black;
}
div {
width: 200px;
height: 200px;
}
</style>
<div></div>

11
image/test/reftest/gif/one-pixel-no-image-data.html Normal file
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@@ -0,0 +1,11 @@
<!DOCTYPE html>
<style>
html{
background-color:black;
}
div {
width: 200px;
height: 200px;
}
</style>
<div style="background-image:url(data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)"></div>

3
image/test/reftest/gif/reftest.list
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@@ -27,3 +27,6 @@ fuzzy-if(Android,0-1,0-8) == tile-transform.html tile-transform-ref.html
# Bug 1234077 # Bug 1234077
== truncated-framerect.html truncated-framerect-ref.html == truncated-framerect.html truncated-framerect-ref.html
# Bug 1801397
== one-pixel-no-image-data.html one-pixel-no-image-data-ref.html