[Webkit-unassigned] [Bug 92847] New: REGRESSION(r123893): Reftest mismatches are run through ImageDiff with 0.1 tolerance

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=92847

           Summary: REGRESSION(r123893): Reftest mismatches are run
                    through ImageDiff with 0.1 tolerance
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Tools / Tests
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: zandobersek at gmail.com
                CC: dpranke at chromium.org


After r123893[1] and the image diffing code refactoring, the default tolerance is set to 0.1 for the port when diffing images[2]. With the tolerance for diffing reftest output being 0, the expression on the next line[3] evaluates to 0.1. This means the ImageDiff operates with 0.1 tolerance, which can lead to false positives (i.e. ImageDiff reports that the two images' differences are within the allowed boundaries).

I guess it should explicitly be checked whether the tolerance argument passed into base.diff_image is None and act accordingly. I don't know why the default value for the tolerance option is being overridden, though (if it is actually overridden rather than just ensured it exists).


[1] - http://trac.webkit.org/changeset/123893
[2] - http://trac.webkit.org/browser/trunk/Tools/Scripts/webkitpy/layout_tests/port/base.py?rev=123893#L325
[2] - http://trac.webkit.org/browser/trunk/Tools/Scripts/webkitpy/layout_tests/port/base.py?rev=123893#L326

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