actionscript 3 - AS3 Rotate an object around its center point

Question

I want this object to rotate around its center rather than the top left corner. The code looks like this:

        switch (event.keyCode)
        {
            case 37:
            car.rotation = -90;
               car.x -= 5;
               break;

So when i press the left key, the car turns left but as it is now it jumps up a bit because its rotating around the top corner.

Thanks

Answer 1

The following will rotate around center :

public function rotateAroundCenter(object:DisplayObject, angleDegrees:Number):void {
    if (object.rotation == angleDegrees) {
        return;
    }
        
    var matrix:Matrix = object.transform.matrix;
    var rect:Rectangle = object.getBounds(object.parent);
    var centerX = rect.left + (rect.width / 2);
    var centerY = rect.top + (rect.height / 2);
    matrix.translate(-centerX, -centerY);
    matrix.rotate((angleDegrees / 180) * Math.PI);
    matrix.translate(centerX, centerY);
    object.transform.matrix = matrix;
    
    object.rotation = Math.round(object.rotation);
}
    

It translates the center of the object to 0,0 then rotate it and then translate it back.