[Webkit-unassigned] [Bug 258672] New: Regression: Canvas Layering of Images Renders Differently

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=258672

            Bug ID: 258672
           Summary: Regression: Canvas Layering of Images Renders
                    Differently
           Product: WebKit
           Version: Safari 17
          Hardware: iPhone / iPad
                OS: Other
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Canvas
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: heystoneybatter at gmail.com
                CC: dino at apple.com

Created attachment 466866

  --> https://bugs.webkit.org/attachment.cgi?id=466866&action=review

Image showing comparison of the two renderings (prior Safari vs 17.0 Beta 2)

Overview:
I was testing the new iPadOS 17.0 Beta 2 (21A5268h) and noticed a bug in how Canvas rendered layered images. I hadn't noticed this issue in 17 Beta 1 (or any prior version of Safari/WebKit), so I believe it was introduced in Beta 2.

The bug can be seen at this URL using an iPad on 17.0 Beta 2:
https://webkit-canvas-test.pages.dev


Steps To Reproduce:
The code at the link above loads a photo of a man (man.jpeg) to the canvas and then loads another image (noise.png) on top of that. The second image is of a subtle noise pattern that should render across the canvas.

Actual Results:
On iPadOS 17 Beta 2, the canvas renders a man covered in an INTENSE noise pattern. It is almost as if globalCompositeOperation is something other than the default.

What You Should See: 
All prior versions of Safari/Webkit will just show a man holding a frying pan with a subtle amount of noise on the image (see attached). The latest Safari Technology Preview release 173 on my MacBook Pro renders this correctly as well. I do not have an iPhone to test on this release yet though, so the bug may be on both iOS and iPadOS.

Build:
Issues seen on iPadOS 17.0 (21A5268h) on an iPad Mini 6th Generation

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