ASSIGNMENT NUMBER 4

Instructor: Sugata Ghosal

Email: gsugata@in.ibm.com

1. Histogram Equalization

(a) Read in the ppm file, attached with this message. What is the dimension of the this image?

(b) Write a program that generates the histogram of this image. User should be able to interactively specify the number of levels in the histogram. Plot the histograms for number of levels=32 and 64.

(c) Write a histogram normalization program. Again the user should be able to specify the number of levels in the histogram.

(d) Plot the histogram for the histogram normalized image for number of levels=32 and 64. How uniform are the resulting histograms? Show the histogram equalized images for number of levels=32, 64 and 128.

(e) What are your conclusions from these experiments.

2. Constrained LS restoration

(a) Write a program to convolve the attached image in the freuquency domain with a lowpass filter

h(x,y)=exp(-(x*x+y*y)/1800).

(b) Take the inverse FFT and show the blurred image g(x,y).

(c) Add noise drawn from a uniform distribution in the interval [0, 10] to the attached image. Normalize the intensity values of the noisy image between 0 and 255. Show the noisy image.

(d) Write a program to perform inverse filtering (set gamma=0 in Equation 5.6-18), and show the restored image.

(e) Write a program to perform contrained LS restoration with accuracy factor a=0.01||n||*||n||,

and show the restored image.

(f) What are your conclusions from the above experiments.