One question, if i scale 1/2 by averaging pixels and plot the interpolation kernel, would it just be a pulse at +-1 with amplitude of 1?

Thanks. ]]>

Thanks you Steve! ]]>

Nice series on aliasing!

I think the key here is to understand that the two low-pass filters (interpolation filter of step 1 and blurring filter of step 2) have the same shape but different width. When multiplied in the Fourier domain, they lead to a single low-pass filter that is the narrower of the two (wider in the spatial domain). Thus, if filter #2 is wider, you use that one, otherwise you use #1. This is why you can simply make the interpolation filter wider when down-sampling, and don’t change anything when up-sampling.

]]>The reason is that you actually acquire the image in Fourier space; frequency sampling density corresponds to field-of-view. Insufficient sampling gives an image that’s too small, leading too aliasing.

]]>Don’t sell your students short. If they understand the concept of aliasing, the vocabulary will be no problem.

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