Sample Question 1
You are given 6 sample images, each containing either Object A or Object B. The feature
vector representation of the objects in the image is given below:
Image No.
1
2
3
4
5
6
Feature vector
[24, 99]
[21, 80]
[23, 101]
[120, 35]
[111, 34]
[123, 43]
Object in the Image
Object A
Object A
Object A
Object B
Object B
Object B
You have decided to use the Euclidean Distance to find the difference between two
feature vectors.
EuclideanDist 
n
 a
i 1
(a)
 bi 
2
i
In comparing two feature vectors, the Euclidean Distance calculation will
eventually give you a number. How do you interpret this number (i.e. what does
it mean if the number is small / large)?
[2 points]
Answer:
The smaller the number, the similar the two objects are.
(b)
You are given an image with the following feature vector:
I = [40, 66]
Try to classify the image (i.e. say that whether it contains Object A or Object B)
using nearest neighbor method. Show your calculation and give reason for your
classification.
[6 points]
Answer:
Compare with Image 1: 36.7
Compare with Image 2: 23.6
Compare with Image 3: 38.9
Compare with Image 4: 85.8
Compare with Image 5: 77.9
Compare with Image 6: 86.1
Conclusion: Image I is most similar to image 2. Since image 2 contains Object A,
then image I must contain object A as well.
(c)
Using the same feature vector as in part (b), try to re-classify the image, but now
using the nearest centroid method. Do you get the same result?
[7 points]
Answer:
Centroid for A: [23, 93]
Centroid for B: [118, 37]
Compare with Centroid A: 31.9
Compare with Centroid B: 83.2
Yes, the result is the same.
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Semester 2 2006/2007
Image Processing