[whatwg] Enabling LCD Text and antialiasing in canvas

[Robert O'Callahan]

On Thu, Mar 14, 2013 at 8:04 AM, Gregg Tavares <gman at google.com> wrote:

> It seems like an opaque canvas should be an orthogonal issue to
> subpixel-aa. Subpixel AA seems like it should be a Canvas2DRenderingContext
> setting though maybe with a name like
>
>    ctx.antialiasingRenderQuality =
>
> With options of
>
>    none
>    grayscale
>    bestForDeviceIfAxisAlignedAndNotScaledOrBlended
>

Ugh!


> This would let the developer choose. It would be clear what the limits
> are, when to use it, and would let the developer choose what they need,
> even in an opaque canvas.
>

Then we would need to come up with a spec for what happens when you
composite subpixel AA over non-opaque pixels, including how the per-channel
alpha values are combined to form a single alpha value. IIRC in some cases
(D2D) you just can't do it.

If we said that in a non-opaque canvas, subpixel AA is treated as
grayscale, that would be OK.

Rob
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