像素级的碰撞测试

var tx, ty;
mc1.buttonMode = true;
mc1.addEventListener("mouseDown", mousedownHandler);
mc2.gotoAndStop(1);

var bmd1 = new BitmapData(mc1.width, mc1.height, true, 0);
bmd1.draw(mc1);
var bmd2 = new BitmapData(mc2.width, mc2.height, true, 0);
bmd2.draw(mc2);

function mousedownHandler(e){
tx = e.stageX - mc1.x;
ty = e.stageY - mc1.y;
stage.addEventListener("mouseMove", mousemoveHandler);
stage.addEventListener("mouseUp", mouseupHandler);
}

function mousemoveHandler(e){
mc1.x = e.stageX - tx;
mc1.y = e.stageY - ty;
if(bmd1.hitTest(new Point(mc1.x, mc1.y), 0x55, bmd2, new Point(mc2.x, mc2.y))){
mc2.gotoAndStop(2);
}else{
mc2.gotoAndStop(1);
}
}

function mouseupHandler(e){
stage.removeEventListener("mouseMove", mousemoveHandler);
stage.removeEventListener("mouseUp", mouseupHandler);
}