2D FFT of an image shows some invalid values for high frequencies
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I uploaded my 2D FFT magnitude image here:
If you take a look at it, for high frequencies[right, left, top and bottom], only at around x and y axis, there are some points with high power[yellow color]. These points shouldn't be in the resultant FFT2, since I know the original height image is isotropic and therefore the 2D FFT must look something like the example below(just note high frequencies; they are not for the same image):
Now, the question is, what could be the possible reasons for such a behavior at high frequencies?
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Matt J
2013-6-27
编辑:Matt J
2013-6-27
since I know the original height image is isotropic and therefore the 2D FFT must look something like the example below
Post the original height image, so that we can verify that it is isotropic.
Have you used 'axis equal' to display these images? I can discern some asymmetry in your 2nd FFT image, even though it is mostly isotropic.
回答(2 个)
Matt J
2013-6-27
Now, the question is, what could be the possible reasons for such a behavior at high frequencies?
Because the frequencies you've shown are not really "high". Both plots look the same, except that the first one has smaller axis limits and is presenting a cropped view of the 2nd one.
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