[SciPy-User] ifft on images, symmetry artifacts?

Joe Barfett joebarfett@yahoo...
Mon Jan 11 18:18:07 CST 2010


Hello,
I'm using scipy (numpy.fft.fft2) to transform an image into the frequency domain. Then by using numpy.fft.ifft2 to transform the same image back into the spatial domain, I find that I get symmetry in the image around a reflection line (and not the original image).
Google has revealed websites like this one: http://www.rzuser.uni-heidelberg.de/~ge6/Programing/convolution.html
This is the code snippet they use:
def Convolution(image1,image2):
	""" Simple convolution example """
	fftimage = fft2(image1)*fft2(image2)
	return ifft2(fftimage).real
#end of Convolution
which uses ifft but generates appropriate output. They do however only use the real component of the frequency domain image. I find the exact same approach does not work in my case, but rather gives these weird symmetries. 
It's been a few weeks of hacking and I would really appreciate the guidance of someone more experienced than me. Thanks a great deal if you know the answer!
joe 




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