- Download your class image, convert it to grayscale (see lenna and the example referenced there to see how to convert to grayscale), embed it into a 256 x 256 (or 512 x 512) array, and find its Fourier Transform. You should take the square root of the input before transforming so that an eventual inverse transform will restore the original irradiance. See Fourier transform example)
- Mask your image so that it has circular (or elliptical) borders instead of square borders. Zero fill the exterior. Find its Fourier Transform and compare with the results of the previous exercise.
- Use your class image to show examples of lowpass, highpass, and bandpass operations. See ( Filtering in the Frequency Domain)
- Use one of your classmate's images and interchange the magnitude of the Fourier transform of one image with the phase of the other. You should see that the resulting inverse transform follows the phase information.
- Convert your class image to grayscale and then to a phase image. Process the phase image to recover the underlying image. Compare different forms of phase contrast filtering. (See examples)

Maintained b*y* John
Loomis, last updated *25 July 2012 *