private void Manip_ManipulationUpdate(object sender, ManipulationGestureEventArgs e)
        {
            var postit = sender as Postit;

            var matrix = (postit.RenderTransform != null) ? postit.RenderTransform.Value : new Matrix();

            Point ct = new Point(postit.RenderSize.Width / 2, postit.RenderSize.Height / 2);
            // transform it to take into account transforms from previous manipulations 
            ct = matrix.Transform(ct);
            //this will be a Zoom. 
            matrix.ScaleAt(e.Delta.ScaleX, e.Delta.ScaleY, ct.X, ct.Y);
            // Rotation 
            matrix.RotateAt(Geometry2DHelper.RadiansToDegree(e.Delta.Rotation), ct.X, ct.Y);
            //Translation (pan) 
            matrix.Translate(e.Delta.TranslationX, e.Delta.TranslationY);

            postit.RenderTransform = new MatrixTransform(matrix);
        }
 void manip_ManipulationUpdate(object sender, ManipulationGestureEventArgs e)
 {
     e.ApplyDeltaOnRenderTransform();
 }