drawScale = function() {
		var offset;
		var length;

		ctx.lineWidth = 1;
		ctx.fillStyle = options.scaleColor;

		ctx.save();
		for (var i = 24; i > 0; --i) {
			if (i % 6 === 0) {
				length = options.scaleLength;
				offset = 0;
			} else {
				length = options.scaleLength * 0.6;
				offset = options.scaleLength - length;
			}
			ctx.fillRect(-options.size/2 + offset, 0, length, 1);
			ctx.rotate(Math.PI / 12);
		}
		ctx.restore();
	}
Draw the scale of the chart