[whatwg] [canvas] inner shadows

Glenn Maynard glenn at zewt.org
Sat Nov 24 07:59:26 PST 2012

On Fri, Nov 23, 2012 at 11:11 PM, Rik Cabanier <cabanier at gmail.com> wrote:

> What matters is the shape that is used to calculate the blur (step 1)
> In your example, that shape is a rectangle so just the rectangle edges will
> be blurred.
> That slightly blurred rectangle is then composited with the clipping region
> in step 4.
> The end result is a solid rectangle in the shadowcolor that composites on
> top of the shape.

Testing with Hixie's code (https://zewt.org/~glenn/canvas-glow.html), the
output is very close to "inner shadow" in Photoshop (distance 0, size 22):

(I'm testing against inner shadow instead of inner glow; inner glow seems
to do something a little more complex at the blur step than a gaussian
blur.  Tested in Chrome 21; output in Firefox is different, but I probably
need to update.)

Glenn Maynard

More information about the whatwg mailing list