Fix the definition of pixelated for createImageBitmap.

[schenney-chromium]

The definition of pixelated image scaling in https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#dom-resizequality-pixelated was broken by an earlier edit. Fix it by adopting the CSS definition of pixelated from https://drafts.csswg.org/css-images-3/#valdef-image-rendering-pixelated. Effort was made to integrate the CSS definition into the existing content (createImageBitmap does not support the same set of smoothing options as CSS)..

Fixed: #3485

• At least two implementers are interested (and none opposed):
  • All browsers implement this and the spec should match the intent.
• Tests are written and can be reviewed and commented upon at:
  • WPT html/canvas/element/manual/imagebitmap/canvas-createImageBitmap-resize.html
• Implementation bugs are filed:
  • N/A
• MDN issue is filed: N/A
• The top of this comment includes a clear commit message to use.

---

/imagebitmap-and-animations.html ( diff )

[annevk]

This should probably be located together with the enum value definition above.

Also, in the note directly above this it says that for pixelated there is a specific algorithm, which doesn't really appear to be the case. We should probably fix that while here.

[schenney-chromium]

I can certainly move it up with the enum. I was unsure where to put it.

Pixelated is more specific than the others, but I agree it is not fully defined. Could I address that by changing "... using an interpolation method." to "... using bilinear interpolation." The latter is the actual intent.

Or am I misunderstanding and you're saying it's not formatted as an algorithm with numbered steps etc. I could do that too.

[annevk]

If you specify the interpolation method I think that's clear enough for now.

At some point what happens should be defined as part of the overall algorithm that manipulates an image, but that's the larger rewrite I failed at completing many years ago. 😅

[schenney-chromium]

Thanks. New version up that I think addresses the issues.

[schenney-chromium]

Ping. Just trying to wrap things up.

[domenic]

I'm unable to push my editorial tweaks because "Allow edits from maintainers" is not checked for this PR. Can you enable that?

[schenney-chromium]

I'm not seeing the checkbox to allow edits in the location that GiitHub docs say it should exist (below the Notifications component). Am I missing something? Is there another way to communicate the edits?

[domenic]

The reason it's not on by default is because you're doing this from an organizational fork instead of an individual one. But in the past other Igalians like @Ms2ger have succeeded in finding and checking the box...

Anyway, I'll just give you the diff instead.

iff --git a/source b/source
index 12624faf..17ae0c22 100644
--- a/source
+++ b/source
@@ -115842,11 +115842,10 @@ <h3 split-filename="imagebitmap-and-animations">Images</h3>
   smoothing as necessary to avoid distorting the image when the target size is not a clean multiple
   of the original.</p>
 
-  <p>To implement "<span data-x="dom-ResizeQuality-pixelated">pixelated</span>", for each axis
-  independently, first determine the integer multiple of its natural size that
-  puts it closest to the target size and is greater than zero. Scale it to this
-  integer-multiple-size using nearest neighbor, then scale it the rest of the way to the target
-  size using bilinear interpolation.</p>
+  <p>To implement "<code data-x="dom-ResizeQuality-pixelated">pixelated</code>", for each axis
+  independently, first determine the integer multiple of its natural size that puts it closest to
+  the target size and is greater than zero. Scale it to this integer-multiple-size using nearest
+  neighbor, then scale it the rest of the way to the target size using bilinear interpolation.</p>
 
   <p>The "<dfn enum-value for="ResizeQuality"><code data-x="dom-ResizeQuality-low">low</code></dfn>"
   value indicates a preference for a low level of image interpolation quality. Low-quality image
@@ -115864,7 +115863,8 @@ <h3 split-filename="imagebitmap-and-animations">Images</h3>
   <p class="note">Bilinear scaling is an example of a relatively fast, lower-quality image-smoothing
   algorithm. Bicubic or Lanczos scaling are examples of image-scaling algorithms that produce
   higher-quality output. This specification does not mandate that specific interpolation algorithms
-  be used, except for "<span data-x="dom-ResizeQuality-pixelated">pixelated</span>" as described above.</p>
+  be used, except for "<code data-x="dom-ResizeQuality-pixelated">pixelated</code>" as described
+  above.</p>
 
   </div>

[Ms2ger]

Hm, not sure that I did find the checkbox; I may have had to move my PRs to my own fork. I'll delete the organisational fork once this PR is in. (Grumbles at GitHub)

[schenney-chromium]

OK. Edits applied. Much annoyance with GitHub authentication.