[Webkit-unassigned] [Bug 254202] New: [GPU Process] REGRESSION (261700 at main): Various "css-backgrounds/background-size-" tests fail with pixel differences

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=254202

            Bug ID: 254202
           Summary: [GPU Process] REGRESSION (261700 at main): Various
                    "css-backgrounds/background-size-" tests fail with
                    pixel differences
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: sabouhallawa at apple.com
                CC: bfulgham at webkit.org, simon.fraser at apple.com,
                    zalan at apple.com

There is a slight difference between a frame decoded using CGImageSourceCreateImageAtIndex() and a frame decode using CGImageSourceCreateThumbnailAtIndex(). A thumbnail frame has to be decoded for a certain size which is called sizeForDrawing.

The test page draws a tiled background-image by calling BitmapImage::drawPattern() which ends up calling CGImageSourceCreateImageAtIndex().
The expected page draws an HTMLImageElements by calling BitmapImage::draw() which ends up calling CGImageSourceCreateThumbnailAtIndex().

The fix is to switch back to use CGImageSourceCreateImageAtIndex() for small images. This way we can ensure the image is decoded the same way for both the test and the expected pages.

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