A mathematical operation, related to multiplication, which can be performed on two mathematical functions or images. For imaging, any filter that emphasizes particular spatial frequencies is a type of convolution. Examples include high-pass ”sharpening” filters and low-pass ”smoothing” filters. Convolution is most easily performed by transforming both an image and the desired filter shape using a Fast Fourier Transform (FFT), multiplying them together, and performing an inverse FFT on the result. In other words, multiplication in the frequency domain is equivalent to convolution in the spatial domain. Convolution is the opposite of deconvolution.