rotateOnCenter using Matrix2D logic from 0.7.1

gistfile1.ts

// Rotates a DisplayObject on center by angleInDegrees
        private rotateOnCenter( component:createjs.DisplayObject , x:number , y:number , angleInDegrees:number ):void {
            // Make a new Matrix
            var m = new createjs.Matrix2D( 1 , 0 , 0 , 1 , 0 , 0 );
            // Transform midpoint into matrix space
            var point = new createjs.Point( 0 , 0 );
            point = m.transformPoint( x , y , point );
            // Translate matrix by point to center component on matrix
            m.tx -= point.x;
            m.ty -= point.y;
            // (Counter)rotate component by input degrees
            m.rotate( angleInDegrees * ( Math.PI/180.0 ) );
            // Translate component back to position in matrix
            m.tx += point.x;
            m.ty += point.y;
            // Apply component matrix to rotation matrix
            m.prependMatrix( component.getMatrix(null) );
            // Apply combined matrix to component
            m.decompose( component );
        }