html5-canvas Compositing Clip images inside shapes with "source-in"
Example
context.globalCompositeOperation = "source-in";
source-in compositing clips new drawings inside an existing shape.
Note: Any part of the new drawing that falls outside the existing drawing is erased.
context.drawImage(oval,0,0);
context.globalCompositeOperation='source-in'; // picture clipped inside oval
context.drawImage(picture,0,0);
