[Webkit-unassigned] [Bug 203250] New: PNG images produced for some reftests have different hash even when the pixels inside the image are the same.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=203250

            Bug ID: 203250
           Summary: PNG images produced for some reftests have different
                    hash even when the pixels inside the image are the
                    same.
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Images
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: clopez at igalia.com
                CC: bugs-noreply at webkitgtk.org

It happens for example with the test css/css-color/hsl-005.html from WPT.

This test can be run from WPT (via WebDriver) with the command:

./wpt run webkitgtk_minibrowser css/css-color/hsl-005.html

Or it can be run also with the usal layout tests runner, with for example:

Tools/Scripts/run-webkit-tests --release --gtk imported/w3c/web-platform-tests/css/css-color/hsl-005.html


The expected image produced by this test has a different hash than the one of the reference.
However, when you check the pixel differences inside the images you find that the pixels are exactly equal.


It has been suggested this may be related to some timestamp (or something similar) that the screenshooting code writes into the png image,
but I don't think that is the case because:

 - The expected PNG image you get, even when different in hash from the original, is the same always
   (if you run it at different times)
 - If you copy hsl-005.html over hsl-005-expected.html (or viceversa) then the hashes of the images match always.
   That indicates IMHO that the issue that causes different hashes is not on the screenshooting code itself.


This is currently not an issue when running the layout tests, because the tooling
fallbacks to do a pixel comparasion when the hash of the images don't match.

But it can be an issue for another test suites like WPT.
Related: https://github.com/web-platform-tests/wpt/pull/19825


It would be nice if the PNG image produced has the same hashes when the contents of the pixels are the same

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20191022/3289d202/attachment.html>