Better method for rendering AA ellipses.

This uses the standard ellipse equation as a signed distance 
test, and adjusts the result by the length of the gradient 
at that point to get a better approximation of the distance 
to the ellipse. It replaces the standard ellipse and 
roundrect shader renderers.

Also adds a check to see if the curvature extrema of the 
stroke are less than the curvature extrema of the ellipse (i.e. 
the radius of curvature is larger). In this case, it's no 
longer an ellipse and we can't use this renderer.

Committed: http://code.google.com/p/skia/source/detail?r=9016

R=bsalomon@google.com, robertphillips@google.com

Author: jvanverth@google.com

Review URL: https://chromiumcodereview.appspot.com/14938004

git-svn-id: http://skia.googlecode.com/svn/trunk@9055 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed