Why image is converted to frequency domain -


in filters of image processing, see image converted spatial domain frequency domain. question is: why that? different between image in spatial domain , image in frequency domain ?

this done performance reasons. filtering in spatial domain convolution, o(n^2), whereas in frequency domain convolution becomes multiplication, o(n). small filters (small n) cost of fft to/from frequency domain relatively large, , filtering performed directly, using convolution. larger filters (larger n), balance tips in favour of filtering in frequency domain, since cost of fft becomes relatively small compared o(n^2) operation.


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