They developed a package called PerSketch, which was designed for line-drawings, not for regular images but for line drawings of the kind shown here, where you have cartoon like figures and they are used for illustrating things. So here in the first drawing on the left side we have a circle and a rectangle and the package allows for the circle and the rectangle for that matter any figure to be moved. These figures can be moved, for example circles can be brought near the rectangle, so that a circle over left as the result what we get is a combination and now there are more primitives than just a circle and a rectangle in fact the system then can converte this combination of figures into more primitive description, then you can for example have semi-circles, or you can have access to the individual line segments, and you can eliminate them.
