An Introduction to Fourier Theory - http://gershwin.ens.fr/vdaniel/Doc-Locale/Cours-Mirrored/Maths-Stuff/fourier/
A mathematically inclined introduction with illustrations and explanations of related theorems, its properties and numerical methods for calculating transforms. |
Fast Fourier Transform - http://mathworld.wolfram.com/FastFourierTransform.html
Article in MathWorld. |
Fast Fourier Transforms - http://en.wikipedia.org/wiki/Fast_Fourier_transform
Survey and history of FFT algorithms from Wikipedia. |
Introduction To Fourier Transform - http://www.rnowik.com/document.php?id=7
A description of the principle of fourier transform and subsequent derivation of formulae. Page includes graphs. |
Introduction to the Fourier Transform - http://www.cs.unm.edu/~brayer/vision/fourier.html
Notes on applications to Image Processing. |