[whatwg] Canvas: clarification of compositing operations needed
leodutra.br at gmail.com
Thu Jul 29 07:17:52 PDT 2010
People have a very strong feeling about Firefox. This is beautiful, but not
good to it. Firefox is now, over the Windows 7 and Mac, the slowest browser.
an extension and Firefox eats CPU when we run any game built using HTML
But this is not the point.
*"**Composite **A** within the clipping region over the current canvas
bitmap using the current composition operator."*
The word "clipping" is the point. I am very sad that input type="color" does
not cite the need of a color picker. But This part, is completely bright.
That's why Microsoft agree with Chrome, Chrome with Safari (they don't agree
sometimes) and Opera presents that way too.
2010/7/29 David Flanagan <david at davidflanagan.com>
> James Robinson wrote:
>> On Wed, Jul 28, 2010 at 2:46 PM, Tab Atkins Jr. <jackalmage at gmail.com<mailto:
>> jackalmage at gmail.com>> wrote:
>> On Wed, Jul 28, 2010 at 2:43 PM, David Flanagan
>> <david at davidflanagan.com <mailto:david at davidflanagan.com>> wrote:
>> > Firefox and Chrome disagree about the implementation of the
>> > destination-atop, source-in, destination-in, and source-out
>> > operators. Test code is attached.
>> I don't think your attachment made it through.
>> https://developer.mozilla.org/samples/canvas-tutorial/6_1_canvas_composite.htmlshows some of the differences, although it does not cover all cases.
> You didn't miss much. My example was very similar to the one you link to.
>> The spec is certainly clear but that does not make the behavior it
>> specifies good. I find the spec's behavior pretty bizarre and Microsoft has
>> expressed a preference for the Safari/Chrome interpretation:
>> http://lists.w3.org/Archives/Public/public-canvas-api/2010AprJun/0046.html- although that thread did not get much discussion.
> Thanks for that link. The thread you reference refers back to an earlier
> thread on this list. My apologies for not finding it and reading it before
> posting again.
> For example, I think
>> drawing a 20x20 image into a 500x500 canvas without scaling with a
>> globalCompositeOperation of 'copy' should result in only the 20x20 region
>> being cleared out, not the entire canvas.
> Yikes! It hadn't occurred to me that copy should behave that way. But
> you're right that that is what the spec requires. Opera does it that way.
> Firefox, thankfully, does not.
> Perhaps independently of the debate over infinite bitmap vs. shape extents,
> we can agree that "copy" is a special value that means "do not perform
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