[whatwg] getImageData/putImageData comments

Ian Hickson ian at hixie.ch
Fri Jun 12 23:57:03 PDT 2009

On Sat, 13 Jun 2009, Robert O'Callahan wrote:
> On Sat, Jun 13, 2009 at 6:39 AM, Ian Hickson <ian at hixie.ch> wrote:
> > The long and short of this is that if we solve this problem today, the
> > solution will be abused as much as the current API, and we'll have to
> > introduce yet another solution when high-res backing stores are common. So
> > instead I'm hoping that (a) authors won't screw this up, and (b) high-res
> > backing stores will be implemented sooner rather than later. If we fail
> > with (a), which is more likely if (b) is delayed, then we'll just
> > introduce a higher-res API later, and designate this one a lost cause.
> Whether high-resolution backing stores are implemented or not is 
> irrelevant as long as most authors are testing their scripts on systems 
> configured with a 1:1 ratio of CSS pixels to device pixels. So in 
> practice you're also relying on (c) rapid deployment of high-dpi screens 
> to canvas-using Web developers. That's why I think you hope in vain.
> Altering the current API so that it always uses one image-data pixel per 
> CSS pixel would not make it useless. Everything people are currently 
> using it for will continue to work just fine and the visual results will 
> be just as good as what people are currently seeing. It's just that 
> we'll need a new API in the future to take maximum advantage of 
> hardware.

Right, but that would be less optimal than if we could just re-use today's 
API, hence the hope.

There's no practical difference as far as I can tell between hoping that 
we can reuse the API, and then finding we can't, and introducing a second 
API for high-res screens; and just giving up now and saying that it's a 
low-res API, and then adding a second API later when we have high-res 
screens. The effect is more or less the same. Given that, I think it's 
worth at least trying to see if we get away with it and can in fact use 
this API in high-res situations later.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

More information about the whatwg mailing list