Returns the area of the image the user has selected for cropping, using screen coordinates.
Note: ◼Values are in terms of the bitmap. Use XBmp2Scr and YBmp2Scr to convert bitmap values to screen values ◼ScreenPolygon is an array [0..3] of type, TDPoint. Item 0 is Top-Left, item 1 is Top-Right, item 2 is Bottom-Right and item 3 is Bottom-Left