Feature has no observable effects in primary use cases (drawing), but may constrain implementations in suboptimal ways. E.g., requiring YUV be converted to RGB. See https://github.com/w3c/webcodecs/issues/508 for a more detailed description. Per consensus of WebCodecs spec editors and lack of usage (0.000000339% - 0.00000687% of page loads per a UseCounter in M105), we propose deprecating and removing this feature starting with M108.
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
No.
n/a
M108
Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).
https://github.com/w3c/webcodecs/pull/562Contact emails
dalec...@chromium.org
Explainer
None
Specification
https://github.com/w3c/webcodecs/issues/508
Summary
premultiplyAlpha tells ImageDecoder to multiply the alpha channel into the RGB channels of decoded images. It was added to mirror the capabilities of ImageBitmapOptions, but in retrospect doesn't make sense.Feature has no observable effects in primary use cases (drawing), but may constrain implementations in suboptimal ways. E.g., requiring YUV be converted to RGB. See https://github.com/w3c/webcodecs/issues/508 for a more detailed description. Per consensus of WebCodecs spec editors and lack of usage (0.000000339% - 0.00000687% of page loads per a UseCounter in M105), we propose deprecating and removing this feature starting with M108.
Blink component
Blink>Media>WebCodecs
TAG review
Not applicable
TAG review status
Not applicable
Risks
It's possible that there exists some client which was accessing raw pixel data in JavaScript may observe that the alpha channel is no longer premultiplied into RGB channels. Clients wishing for this functionality can either do the multiply themselves or use createImageBitmap() to do this.
Interoperability and Compatibility
Gecko: Positive Firefox co-editor supports removal.
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On Fri, Sep 16, 2022 at 11:19 PM Dale Curtis <dalec...@chromium.org> wrote:Contact emails
dalec...@chromium.org
Explainer
None
Specification
https://github.com/w3c/webcodecs/issues/508
Summary
premultiplyAlpha tells ImageDecoder to multiply the alpha channel into the RGB channels of decoded images. It was added to mirror the capabilities of ImageBitmapOptions, but in retrospect doesn't make sense.Feature has no observable effects in primary use cases (drawing), but may constrain implementations in suboptimal ways. E.g., requiring YUV be converted to RGB. See https://github.com/w3c/webcodecs/issues/508 for a more detailed description. Per consensus of WebCodecs spec editors and lack of usage (0.000000339% - 0.00000687% of page loads per a UseCounter in M105), we propose deprecating and removing this feature starting with M108.
What would breakage look like? What would happen to callers who still pass that option?
Blink component
Blink>Media>WebCodecs
TAG review
Not applicable
TAG review status
Not applicable
Risks
It's possible that there exists some client which was accessing raw pixel data in JavaScript may observe that the alpha channel is no longer premultiplied into RGB channels. Clients wishing for this functionality can either do the multiply themselves or use createImageBitmap() to do this.
Interoperability and Compatibility
Gecko: Positive Firefox co-editor supports removal.I don't know if we can consider this a Mozilla position. At the same time, this seems small enough to not warrant an explicit issue. (and it's good to have consensus on the issue)
To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfVQSA6gRu8eVfRyu8TPwXQhqduSVDZemsX0%3DGV4nY2jfg%40mail.gmail.com.
To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/096e70e9-197e-4859-3196-6f3277e94f7a%40chromium.org.