Dept. of Electrical and Computer Engineering
EE3015 – Signals and Systems
Discussion Session #9: Image processing using Matlab
In this discussion, we will perform some simple image processing by filtering the Fourier
components of an image using Matlab. This exercise will be graded, and is due next
discussion session, Nov. 1213
. You are required to turn in code and graphs as indicated.
This discussion will be devoted to get started with the assignment, but you are expected
to finish it outside of class.
The submitted work should be your own. You can (and indeed you are encouraged to)
discuss this assignment with other students, but the Matlab code you turn in should
represent your own individual effort.
Preliminaries
We will first load the image file we will work with. Matlab has an image library
containing several images. To load our working image, just type:
>> load clown
This will load an image of a clown into the matrix
X.
This matrix contains a 200 X 320
pixels B/W image. Each element of the matrix represents the intensity of each pixel.
Recall that you can check the dimensions of arrays/matrices with the command
size
.
For
example,
>> size(X)
will report that the
X
matrix that contains the image is of dimensions 200 by 320.
Now we want to visualize this image. Matlab may display it in pseudocolor (different
gray levels are mapped to different colors). You can control the color table by using the
command
>> colormap(gray)
This will use a colormap that consists of a conventional gray scale. Other color maps
include
jet, hot, cool
, etc.
Feel free to try them out. However, for the actual exercise,
colormap(gray)
is more appropriate.
To visualize the image in
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 Fall '08
 Staff
 Digital Signal Processing, Multiplication, Complex number, Highpass filter, Lowpass filter

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