[Webkit-unassigned] [Bug 93171] New: Remove decoding of frames in BitmapImage::frameHasAlphaAtIndex and BitmapImage::frameOrientationAtIndex

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=93171

           Summary: Remove decoding of frames in
                    BitmapImage::frameHasAlphaAtIndex and
                    BitmapImage::frameOrientationAtIndex
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Images
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: hclam at google.com


These two methods shouldn't require full image decoding. They are blockers for having asynchronous / deferred image decoding.

frameOrientationAtIndex

This is not implemented at the moment. And this information can be read from the image header without decoding the entire image.

frameHasAlphaAtIndex

This method is used for optimization in drawing. CG port doesn't return this reliable and use a simple jpeg->no, png/gif->yes heuristic. Having to decoding a full frame to answer this call is too heavy. This also blocks asynchronous image decoding as this is not an essential entry point to kick start image decoding.

We want image decoding to start only when an image is drawn, at least for single frame images.

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