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Re: [whatwg] I believe source rectangles for HTML5 Canvas drawImage are specified incorrectly

From: Robert O'Callahan <robert@ocallahan.org>
Date: Wed, 19 Dec 2012 22:29:23 +1300
Message-ID: <CAOp6jLZsnZqTfo56sBHR+Y3yGNymyHPWdLH+xMe32iJHUg5j=g@mail.gmail.com>
To: Rik Cabanier <cabanier@gmail.com>
Cc: Vladimir Vukicevic <vladimir@pobox.com>, Kevin Gadd <kevin.gadd@gmail.com>, Justin Novosad <junov@chromium.org>, whatwg@lists.whatwg.org, Jeff Muizelaar <jmuizelaar@mozilla.com>, Ian Hickson <ian@hixie.ch>
On Wed, Dec 19, 2012 at 5:39 PM, Rik Cabanier <cabanier@gmail.com> wrote:

> On Tue, Dec 18, 2012 at 1:14 PM, Robert O'Callahan <robert@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
>> needed.
>>
>>
> 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.

Rob
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Received on Wednesday, 19 December 2012 09:29:52 UTC

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