Mimick Photoshop Clone Tool

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I would suggest the following steps

1. 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.
2. Open an image in a window and draw the desired contour on the copy image.
3. Based on the contour, create a mask that can cut out the selection.
4. Now use that roi to place it somewhere else, could also be under mousepoint.
5. Make use of opacity options for a perfect blending.