# Kevin Cowtan's Book of Fourier

This is a book of pictorial 2-d Fourier Transforms. These are
particularly relevant to my own field of x-ray crystallography, but
may also be of interest to anyone involved in signal processing or
frequency domain calculations.
I have adopted a colourful scheme for representing complex numbers on
the two-dimensional images. Amplitude is represented by colour
**saturation** and **brightness**, while phase is given by
**hue**. This is illustrated in the following figure:

Note that positive real numbers are *red*, and negative real
numbers are *cyan*.

### Contents:

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*Kevin Cowtan: cowtan@yorvic.york.ac.uk*