While trying to debug a possible issue with ImageDiff I found that is really hard to run this test manually (without using the layout-test runner). The main issue is that the tool doesn't accept the paths to the images. Instead it expects via stdin the contents of both images (as byte strings), with some fields that tell it how much bytes each image uses on stdin.
Created attachment 381489 [details] Patch
Created attachment 381494 [details] Patch
Comment on attachment 381494 [details] Patch The new Python script looks fine. I think that the failed test case of the “webkitperl” EWS is somewhat intermittent (for example here's another recent failure: https://ews-build.webkit.org/#/builders/19/builds/11760), and it should be fine to land this.
Comment on attachment 381494 [details] Patch Clearing flags on attachment: 381494 Committed r251428: <https://trac.webkit.org/changeset/251428>
All reviewed patches have been landed. Closing bug.
<rdar://problem/56496270>
``` nzimmermann@nzimmermann-macbook WebKit % run-imagediff LayoutTests/svg/foreignObject/body-background-expected.png actual.png Traceback (most recent call last): File "/Users/nzimmermann/Software/GitRepositories/WebKit/Tools/Scripts/run-imagediff", line 70, in <module> image_diff, diff_percent, error = port.diff_image(imageContentA, imageContentB, options.tolerance) TypeError: cannot unpack non-iterable ImageDiffResult object ``` The script is outdated. Shall we update it? Carlos?