Off-screen canvas rendering of a gradient

gistfile1.js

( function () {

	var canvas = document.getElementById( 'stage' ),
		context = stage.getContext( '2d' ),
		gradient = document.createElement( 'canvas' );;

	( function ( size, renderFunction ) {
		var gc = gradient.getContext( '2d' ),
			size = 100,
			half = size / 2,
			glow;

		gradient.width = size;
		gradient.height = size;
		glow = gc.createRadialGradient( half, half, 1, half, half, half );
		glow.addColorStop( 0, 'rgba( 255, 255, 255, 0.5 )' );
		glow.addColorStop( 1, 'rgba( 255, 255 ,255, 0 )' );
		gc.fillStyle = glow;
		gc.fillRect( 0, 0, size, size );
	} )();

	context.drawImage( gradient, 0, 0 );

} )();