By the way, ringing at sharp edges is an intrinsic feature of higher- order spline interpolation, right? I believe this kind of interpolant is really intended for smooth (band-limited) data. I'm not sure why the pre-filtering makes a difference though; I don't yet understand well enough what the pre-filter actually does.
I'm not sure what people normally do in computer graphics, since I'm working more with natural band-limited images, but in the case of Stefan's "rotate_artifacts" example, wouldn't it be appropriate to use the 1st- or 0th-order spline instead of the 2nd order? If your real-life data are smooth enough, however, then in theory the ringing with higher orders should go away. Sorry if I'm stating the obvious and missing the real point! I just wanted to make sure this hasn't been overlooked... Likewise, sorry I didn't mention this before if it does turn out to be relevant. Let me know if you want references to explain what I said above. James. _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion