# IIB: 4F8 Image Processing: 2015-16, Lent Term.

### Joan Lasenby

### Handouts, m-files and Images

Consolidated Handouts 0 to 6 -- Image Processing

Handout 01-- The 2D Fourier Transform etc

- Sinusoid_Demo.m -- illustrates the 2d FT of a 2d sinusoid. As expected, the FT contains just 4 peaks at + and - the 2 frequencies.
- lenna256.mat -- mat file containing the 256x256 image of lenna in the array x.
- grayimage.m -- small program to display grayscale images as used by other programs
- convolution_demo.m -- program to convolve Lenna with a gaussian to illustrate blurring

Handout 2 -- Digitisation, sampling and the 2d-DFT

- For an example of aliasing to produce moire patterns see http://ptolemy.eecs.berkeley.edu/eecs20/week13/moire.html
- Brick Wall image for use in the example sheet moireB.jpg
- Quantiser_demo.m : program to quantise Lenna to a specified number of bits

Handout 3 -- 2D Digital Filters

- imagephasedemo2.m : program to illustrate importance of phase in images by giving amplitude and phase only reconstructions
- imagefilter3_demo.m : filtering of Lenna with three bandpass filters (2 rectangular and one circularly symmetric)
- runbessel.m : program to illustrate the form of the IFT of the ideal circularly symmetric bandpass filter for different upper and lower frequencies.

Handout 4 -- 2D Digital filter design and windowing

- productwindow.m : program to plot the 2d windows formed from the product of 1d windows and their spectra [rectangular, Hamming and Kaiser]
- ProdWindowCircBP.m : program to investigate the effects of windowing, with product window functions [rectangular, Hamming and Kaiser], an ideal circularly symmetric lowpass or bandpass filter. Also show what the effects of such a filter are on Lenna.
- RotatedWindow.m : program to plot the 2d windows and their spectra formed from the rotation of 1d windows [rectangular, Hamming and Kaiser].
- RotWindowCircBP.m : program to investigate the effects of windowing, with rotated window functions [rectangular, Hamming and Kaiser], an ideal circularly symmetric lowpass or bandpass filter. Also show what the effects of such a filter are on Lenna.

Handout 5 -- Image Deconvolution

- Inversefilter_new.m : program to perform inverse filtering
- Wienerfilter.m : program to perform Wiener filtering

Handout 6 -- Deconvolution and image enhancement

- contrastmap.m : illustration of applying a contrast map to an image
- lenna256unequal.mat : constrast mapped version of Lenna
- HistEqual.m : program to perform histogram equalisation

Examples Paper and Solutions :

Tripos Papers and Cribs for 2007 to 2010 can be found here