Fullwings, yes, I am aware of that fact. However, my intention is to have the software use the raw image of the diagram and effectively draw lines on top of it that correspond to the computation in question. This annotated image could then be printed and should in my understanding be legal. After all, what is the difference between a copy of the published diagram with lines produced by manually using a ruler and a pencil and the same diagram where the lines have been generated by software?