
Program: Import reads the original image which is put into the autocolor and
rendered. As an approximation of the derivative the gradient operator is taken
followed by root of the squared x and y component (compute). This is done twice
for the first and second derivative resp. The curvature is approximated in the
next compute by (1 + f' * f') 1.5 / (f'') 2. Finally
the three images are combined via an arrange.