Ok, I will try that... Maybe I should have been more clearly what I intend to get... I had it all working already, just without the scaling issue I get camera images and I let opencv compute min/max values and a centerpoint. Somethimes the camera is rotated in a undesired position so the user should be able to rotate the view, including the measurepoints, and more complex including the point values so that the stay at the points but do not rotate staying readable... I keep trying with qpainter draw