Alpha channel halved when calling CanvasRenderingContext2d clearRect(), drawImage(HTMLCanvasElement)

By design Issue #6768363

Details

Created
Mar 4, 2016
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This issue is public.
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Steps to reproduce

URL:

Repro Steps:

  1. create 2 canvases
  2. draw text with a shadow on A, then call clearRect() to clear the entire canvas. (Canvas A is actually 100% clear at this point)
  3. draw text with shadow on B, then call A.drawImage(B);

Expected Results:

Images on both canvases should have the same alpha. Canvas A and B should have identical images.

Actual Results:

Dev Channel specific:

No

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    Comments and activity

    • Microsoft Edge Team

      Changed Assigned To to “Mara P.”

      Changed Assigned To to “Christian F.”

      Changed Assigned To from “Christian F.” to “Li-Hsin H.”

      Changed Status to “Confirmed”

    • Please disregard this bug. Is mistaken about how the .shadow* properties work, the “problem” was in my code. I thought the Sofie properties should only affect text, but they also affect .drawImage() calls (as intended by the spec)

    • Please disregard this bug. I was mistaken about how the .shadow* properties work, the “problem” was in my code. I thought the shadow properties should only affect text, but they also affect .drawImage() calls (as intended by the spec)

    • Microsoft Edge Team

      Changed Assigned To from “Li-Hsin H.” to “IE S.”

      Changed Status from “Confirmed” to “By design”

    • Hello,

      Thank you for sharing your problem and solution. Please reopen this case if you have new information about this specific issue for us to investigate.

      Best Wishes,
      The MS Edge Team

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