get Scroll Position
Return the point at the center of the zoomed image. The PointF coordinates rangein value between 0 and 1 and the focus point is denoted as a fraction from the leftand top of the view. For example, the top left corner of the image would be (0, 0).And the bottom right corner would be (1, 1).
Return
PointF representing the scroll position of the zoomed image.