clearing circular regions from HTML5 Canvas

Question

It appears the only way to clear a region from a canvas is to use the clearRect() command - I need to clear a circle (I am masking out areas from a filled canvas, point ligh

Answer 1

Where x = left position, y = right position, r = radius, and ctx = your canvas:

function clearCircle( x , y , r ){
    for( var i = 0 ; i < Math.round( Math.PI * r ) ; i++ ){
        var angle = ( i / Math.round( Math.PI * r )) * 360;
        ctx.clearRect( x , y , Math.sin( angle * ( Math.PI / 180 )) * r , Math.cos( angle * ( Math.PI / 180 )) * r );
    }
}