Obtaining image filter from original and filtered image with FFT

Hi,

I have a grayscale original image, and an image obtained by filtering the original with a certain filter. I need to obtain the image of the filter that has been used.

I tried calculating the fft of the two images I have, then inverse fft for the filter:

filter = ifft2 ( fft2(filteredImg)./fft2(OriginalImg));

This does not work, as it gives me something looking like noise:

What is the problem?

[Star Strider]

First, don’t use filter as a variable name. It is the name of a MATLAB function that you may need, and then won’t be able to use.

Second, if you use imfilter on your original image with your identified filter, does it return your original filtered image? If it does, your identified filter is correct.