[Webkit-unassigned] [Bug 248004] New: SVG and Canvas clipping path artifact

Wed Nov 16 17:36:58 PST 2022

https://bugs.webkit.org/show_bug.cgi?id=248004

            Bug ID: 248004
           Summary: SVG and Canvas clipping path artifact
           Product: WebKit
           Version: Safari 16
          Hardware: Mac (Apple Silicon)
                OS: macOS 13
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: SVG
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: jonathan.olson at colorado.edu
                CC: sabouhallawa at apple.com, zimmermann at kde.org

Created attachment 463563

  --> https://bugs.webkit.org/attachment.cgi?id=463563&action=review

An image (black pixel) shows up incorrectly along the top

Overview: Clipping path seems to have an artifact (and incorrectly shows part of an image) along the top of its bounding box. This is reproducible in SVG, but ALSO seems to happen in Canvas (if it would help to record exact Canvas commands to reproduce, let me know.

Steps to reproduce:

View this HTML:
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">

  <title>Bug example</title>
</head>

<body style="background-color: white;">
  <svg width="1012" height="816">
    <defs>
      <clipPath id="clip" clipPathUnits="userSpaceOnUse">
        <path
            d="M -13.41536647912858271070 -48.37424875107316069034 A 51.77079632679519249905 51.77079632679519249905 0 1 0 14.25492059817330492422 51.40158310364876825815 A 54.91238898038498206233 54.91238898038498206233 0 1 0 -15.09447471721803069045 -54.42891745622437582597 Z"></path>
      </clipPath>
    </defs>
    <g transform="matrix(0.98828125000000000000,0,0,0.98828125000000000000,100,100)" clip-path="url(#clip)">
      <image x="-500px" y="-500px" width="1155px" height="1164px"
             xlink:href="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAYAAABytg0kAAAAAXNSR0IArs4c6QAAAAlwSFlzAAAWJQAAFiUBSVIk8AAAABNJREFUCB1jZGBg+A/EDEwgAgQADigBA//q6GsAAAAASUVORK5CYII%3D"></image>
    </g>
  </svg>
</body>
</html>

Actual results: <attached> (incorrect black line along the top)

Expected results: Similar, but without the line along the top.

Build Date & Hardware:

macOS 13.0.1
Version 16.1 (18614.2.9.1.12)
Release 157 (Safari 16.4, WebKit 18615.1.11.7)

Additional information:

Noticed in https://github.com/phetsims/qa/issues/854, seems independent from the other artifact issues.

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