[whatwg] I believe source rectangles for HTML5 Canvas drawImage are specified incorrectly
robert at ocallahan.org
Wed Dec 19 01:29:23 PST 2012
On Wed, Dec 19, 2012 at 5:39 PM, Rik Cabanier <cabanier at gmail.com> wrote:
> On Tue, Dec 18, 2012 at 1:14 PM, Robert O'Callahan <robert at ocallahan.org>wrote:
>> It seems to me a synchronous constructor that creates an ImageBitmap for
>> a subimage of another ImageBitmap (but not other kind of source!) will be
> Did you mean to say a synchronous constructor?
Yes. That's what I said.
> Reading the new spec (
> http://www.whatwg.org/specs/web-apps/current-work/#imagebitmap), I still
> fail to see how this is better than a drawimage with dx=dy=0 and
> dw/dy=canvas width/height
You mean, how is using createImageBitmap better than drawing the input
ImageBitmap into a temporary canvas and then using that canvas instead of
the result of createImageBitmap?
Basically, createImageBitmap is a more direct approach that's easier to
optimize to avoid copying the image data.
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