[Webkit-unassigned] [Bug 237082] New: createImageBitmap cannot premultiply alpha with ImageData

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=237082

            Bug ID: 237082
           Summary: createImageBitmap cannot premultiply alpha with
                    ImageData
           Product: WebKit
           Version: Safari 15
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Canvas
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ashley at scirra.com
                CC: dino at apple.com

Summary: when calling createImageBitmap() with an ImageData and the option premultiplyAlpha: "premultiply", the resulting ImageBitmap still does not have premultiplied alpha. It appears to work correctly with other overloads using Blob, Image and Canvas.

Repro URL: https://downloads.scirra.com/labs/bugs/imagebitmapalpha/

The demo uses createImageBitmap() premultiplying alpha on Blob, Image, Canvas and ImageData. It uses a WebGL context to read the ImageBitmap pixel data back, via texture upload and readback.

In the ImageData case, the texture pixel data still uses unpremultiplied alpha. Look in the console of the repro page and it will log pass/fail results. The ImageData case fails with pixel data [0, 0, 255, 44], with the expected result [0, 0, 44, 44].

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