This chapter deals with the uses of the Fourier transform for altering the spatial characteristics of an image. Up to this point, we have treated images as functions in space—yet there is an entirely different and richly productive way to think of them: as the superimposition of numerous frequencies. Using a mathematical technique called the Fourier transform; we can transform images into an array of frequencies in frequency space, process the image data as frequencies, and then transform the processed array of frequencies back into image space.
In this chapter, you will explore the concepts behind images in frequency space and learn how you can use image processing in the frequency realm to enhance your astronomical images. Frequency space is a mind-bending concept— but it is not necessary to have a complete understanding of the theory to be able to use the concepts behind it. As you work with images in frequency space, you will develop an intuitive feel for Fourier transforms.
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