In this activity, our goal is to eliminate unwanted information in an image by manipulating in the frequency domain. But first, we investigate what the frequency domain looks like for different types of images.
Two dots (1x1 pixel each) was placed equidistant from the center of the 128x128 pixel image. These dots represent a pair of Dirac deltas, which is the Fourier transform of the sine function. The spacing between the two Dirac deltas is twice the frequency of the sine function. Using fft2() on the images containing two Dirac deltas (images at the upper part of Figure 1) produces a matrix containing the inverse Fourier transform. That is why the images at the lower part of the same figure show sine functions of increasing frequency (smaller gap between successive bands) as the spacing between the Dirac deltas is increased.
Figure 1. Pair of Dirac deltas and corresponding inverse Fourier transforms.
In the fo
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