[Webkit-unassigned] [Bug 151261] New: [GTK] ImageDiff should normalize the diff image

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Fri Nov 13 07:07:21 PST 2015


https://bugs.webkit.org/show_bug.cgi?id=151261

            Bug ID: 151261
           Summary: [GTK] ImageDiff should normalize the diff image
    Classification: Unclassified
           Product: WebKit
           Version: Other
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Tools / Tests
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: clopez at igalia.com
                CC: bugs-noreply at webkitgtk.org, lforschler at apple.com,
                    zan at falconsigh.net

I was checking the diff image for the following ref test that is failing by 1-pixel test:

https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20%28Tests%29/r192415%20%2812243%29/imported/blink/fast/canvas/canvas-clip-stack-persistence-diffs.html

As you can check, on the diff image is hard to see what is different (everything looks black).

So I tried to manually to create a diff image using imagemagick as follows:

$ wget https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20%28Tests%29/r192415%20%2812243%29/imported/blink/fast/canvas/canvas-clip-stack-persistence-actual.png
$ wget https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20%28Tests%29/r192415%20%2812243%29/imported/blink/fast/canvas/canvas-clip-stack-persistence-expected.png
$ composite canvas-clip-stack-persistence-expected.png canvas-clip-stack-persistence-actual.png -compose difference diff.png

The diff.png image generated was like the current we produce. Hard to tell if there is any difference or where.

The I normalized the diff image as follows:

$ convert diff.png -auto-level diff_norm.png

Now the diff_norm.png shows clearly where the problem is.

So I think we can teach ImageDiff to auto normalize the diff image.

I see that each ports seems to have its own version of ImageDiff.

I only tested the GTK one, and opening the bug for this one.

A quick grep suggests that other ports are already normalizing the diff image:
$ find Tools/ -type f -iname "imagediff*.*cpp"|xargs grep -i normalize

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