Mostly an excuse to play with, and show off the capabilities of, the rather fabulous Ipython notebook! I have created an Ipython notebook to demonstrate how to use GMT to do spectral analysis on images.
This is demonstrated by pulling wavelengths from images of rippled sandy sediments.
GMT is command-line mapping software for Unix/Linux systems. It's not really designed for spectral analysis in mind, especially not on images, but it is actually a really fast and efficient way of doing it!
This also requires the convert facility provided by Image Magick. Another bodacious tool I couldn't function without.
My notebook can be found here.
Fantastic images of ripples provided by http://skeptic.smugmug.com