[Webkit-unassigned] [Bug 73952] New: canvas/philip/tests/2d.imageData.put.unchanged.html expects putImageData/getImageData to exactly preserve unpremul-alpha pixel values

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=73952

           Summary: canvas/philip/tests/2d.imageData.put.unchanged.html
                    expects putImageData/getImageData to exactly preserve
                    unpremul-alpha pixel values
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
               URL: http://philip.html5.org/tests/canvas/suite/tests/2d.im
                    ageData.put.unchanged.html
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Tools / Tests
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: bsalomon at google.com


This canvas test calls getImageData, makes a copy of the image data, does putImageData at the same location, and then does another getImageData. It fails if there are any differences in the pixel values retrieved by the two getImageDatas. Just below the section of the spec referenced by the test (http://philip.html5.org/tests/canvas/suite/tests/spec.html#testrefs.2d.imageData.unchanged) is this note:

"Due to the lossy nature of converting to and from premultiplied alpha color values, pixels that have just been set using putImageData() might be returned to an equivalent getImageData() as different values."

It seems that the test should perform a fuzzy comparison.

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