I would suggest the following steps
- Couple a mouse handler to your mousepointer for a specific window, let it store all points that you click forming a contour and draw it while you are doing it.
- Open an image in a window and draw the desired contour on the copy image.
- Based on the contour, create a mask that can cut out the selection.
- Now use that roi to place it somewhere else, could also be under mousepoint.
- Make use of opacity options for a perfect blending.
