Introduction to Spectral Techniques

The following three chapters deal with the representation and analysis of images in the frequency domain, based on the decomposition of image signals into sine and cosine functions—which are also known as harmonic functions—using the well-known Fourier transform. Students often consider this a difficult topic, mainly because of its mathematical flavor and that its practical applications are not immediately obvious. Indeed, most common operations and methods in digital image processing can be sufficiently described in the original signal or image space without even mentioning spectral techniques. This is the reason why we pick up this topic relatively late in this text.