[whatwg] Need clarification on DOM exceptions thrown by canvas 2D drawImage

Justin Novosad junov at chromium.org
Tue Aug 9 08:29:34 PDT 2011

Thanks Philip, that really cleared things up for me.

Any chance you might adjust the 2d.drawImage.outsidesource.html test
to reflect this change in the spec?

> because of the filtering requirements. If CoreGraphics can't do that
> then it's broken (per the spec) regardless of how source rectangles
> are handled. Or is it able to do clamp-to-edge fine up to the edge of
> the source image, just not extend that beyond the image when the
> source rectangle is expanded further?

I second that. And in support of the spec, let me just say that the
clamp-to-edge is essential for many existing canvas-based games that
use large images as sprite maps.  Without clamping to the edge of the
source rectangle you would get color bleeding between adjacent sprites
when the draw operation magnifies the sprite, or even just when it is
not perfectly pixel-aligned.


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