bmd = document.getElementById("canvas").bitmapData;

lenna = new Image();
lenna.src = "res/lenna-300x300.png";

clipping = new Rectangle(10, 10, 280, 280);
rotoMatrix = new Matrix(1, 0, 0, 1, 150, 150);

zoomMax = 0.2;
zoomMin = -0.4;
dz = 0.015;
dr= 0.01;
angle = 0;
zoom = zoomMin;
isZoomIncreasing = true;

setInterval(function() {
	if ( isZoomIncreasing )	zoom = zoom + dz;
	else zoom = zoom - dz;	

	angle = angle + dr;

	if ( angle > 360 ) angle = 0;

	if ( zoom > zoomMax ) {
		isZoomIncreasing = false;
		zoom = zoomMax;
	} else if ( zoom < zoomMin ) {
		isZoomIncreasing = true;
		zoom = zoomMin;
	}

	rotoMatrix.a = Math.cos(angle) * zoom;
	rotoMatrix.b = Math.sin(angle);
	rotoMatrix.c = -Math.sin(angle);
	rotoMatrix.d = Math.cos(angle) * zoom;


	bmd.draw(lenna, rotoMatrix, null, null, null);
}, 20);