[webkit-dev] Feature announcement: canvas pixel access API additions for high-resolution backing stores

Darin Fisher darin at chromium.org
Mon Apr 16 10:52:52 PDT 2012

Could this be an opportunity to design an asynchronous API for fetching the
pixel buffer?  It seems like many implementations are GPU backed now, and
fetching the pixel buffer is an expensive (blocking) operation.  Had you
considered making such a change?


On Thu, Apr 12, 2012 at 6:17 PM, Dan Bernstein <mitz at apple.com> wrote:

> [This is actually an enhancement announcement to an existing feature]
> Over at <
> http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2012-March/035112.html>,
> Edward O’Connor has proposed enhancements to CanvasRenderingContext2D to
> allow authors to take full advantage of high-resolution backing stores,
> when available (whereas the existing API hides the fact that the backing
> store resolution is not CSS pixel resolution, for compatibility with
> existing content). The enhancements include a backingStorePixelRatio
> attribute and {get,put}ImageDataHD functions on CanvasRenderingContext2D.
> Through <https://bugs.webkit.org/show_bug.cgi?id=83619> and <
> https://bugs.webkit.org/show_bug.cgi?id=83836>, I am making these
> enhancements, with the names prefixed with “webkit”.
> There is no build-time option to disable these enhancements. Ports that
> don’t opt into ENABLE_HIGH_DPI_CANVAS get a working, albeit boring, version
> of the additional API. Ports that opt into high-DPI canvas need to enhance
> their ImageBuffer implementation to fully support the resolutionScale and
> CoordinateSystem parameters.
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> webkit-dev at lists.webkit.org
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