CS 519 — Signal and Image Processing
Program #2
Due date: Friday, April 25, 2003
Programming: This programming assignment consists of three major parts (corresponding to topics dis-
cussed in Chapters 6, 8 and 9 with some of Chapter 7 thrown into part C). Each part can be (but doesn’t
have to be) implemented as a separate program, in which case you would have three subdirectories (such
as prog2a, prog2b, and prog2c) within the directory for this assignment. This assignment will be
submitted online in the same way as was Program #1 (make sure you tar up everything in you assignment
directory, including your write-up and any images, or preferably links to them).
A) Write a function (or class) to perform histogram equalization and test it on the image
/usr/local/classes/cs/cs519/images/mystery.pgm
Display the original image, its histogram, the histogram equalized image, and the equalized histo-
gram. The two images should be displayed side-by-side in a single window (using a QHBox, for
example) with the original image on the left and the equalized image on the right. The two histograms
should also be displayed side-by-side in a single window (but in a different window than the images)
with the original histogram on the left. (10 pts)
B) Write a function that rotates an image around its center by a specified angle. Recall that rotation about
a point (other than the origin) is given by Eq. (16) in Chapter 8 of the textbook. Use backwards map-
ping (i.e., take the inverse of the resulting transformation matrix) and bilinear interpolation. Put the
resulting (rotated) image into an image of size D × D where D is the image diagonal length. Allow the
rotation operation to be applied to the original or rotated image (thus rotating it even further). Display
the rotated image either next to the original or in a separate window. You may choose any full color
(RGB) image that is available in the course’s “images” directory. (Again, to save disk space and
prevent large submissions, try to use symbolic links to images when possible). (15 pts)
C) Write a function that convolves an image I with a convolution kernel. The image
/usr/local/classes/cs/cs519/images/desktop.pgm
is to be convolved with both of the following kernels
10-1 121
gx=20-2 gy=000
1 0 -1 -1 -2 -1
and the two images Ix = I * gx and Iy = I * gy resulting from the two convolutions are to be combined
and scaled (to values between 0 and 255) by computing
where
G
′
255
Gmax Gmin
–
------------------------------GG
min
–()=
G
Ix
2
Iy
2
+=
