[whatwg] CSS Filter Effects for Canvas 2D Context

[Tab Atkins Jr.]

On Wed, Jan 25, 2012 at 6:41 AM, David Geary <david.mark.geary at gmail.com> wrote:
> On Tue, Jan 24, 2012 at 5:22 PM, Chris Marrin <cmarrin at apple.com> wrote:
>> Adding filter functions to canvas would require you to re-render the items
>> for every filter change and you'd have to animate it all yourself.
>
> Sure, but you must create a superfluous canvas for each set of images that
> you animate, and invoke an entirely different technology to apply the
> filter. You must  make sure that those superfluous canvases have
> transparent backgrounds, no borders, and have the correct Z order so they
> appear over, and not under, the primary canvas for the application. And I'm
> sure there are other gotchas to this hybrid approach that don't immediately
> come to mind.
>
> I'd much rather use the filtering underlying API and control the rendering
> and animation myself.

Yes, it's effectively creating an ad-hoc retained-mode API out of
multiple <canvas> elements solely so it can apply filtering.

(Using multiple backing canvases to sprite things is a reasonable
performance hack, but I don't think it should be required for basic
functionality.)

~TJ