[whatwg] [canvas] request for {create, get, put}ImageDataHD and ctx.backingStorePixelRatio

[Charles Pritchard]

On 3/20/2012 12:08 PM, Boris Zbarsky wrote:
> On 3/20/12 3:00 PM, James Robinson wrote:
>> If we are adding new APIs for manipulating the backing directly, can we
>> make them asynchronous? This would allow for many optimization
>> opportunities that are currently difficult or impossible.
>
> You mean like not blocking the world on the readback?
>
> That would indeed be very nice.  The question is what happens if 
> drawing happens after the getImageData call...  Or for that matter 
> after the putImageData call (though I suspect there's less need for 
> putImageData to be async).

I recommend we complete+use RoC's media processing API in addition to 
the CSS shaders proposal:
http://www.w3.org/TR/streamproc/
https://dvcs.w3.org/hg/FXTF/raw-file/tip/custom/index.html

This would allow async post-processing via workers and less worry about 
putImage semantics.

If we're looking for async getImageData purely for recognition, I think 
the current postMessage transfer semantics sped things up enough.

getImageData and a subsequent draw call are always going to need to grab 
more memory. async isn't going to change that.

-Charles