digital image processing using matlab: filters
TRANSCRIPT
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NATIONAL CHENG KUNG UNIVERSITY
Inst. of Manufacturing Information & Systems
DIP & SOFTWARE IMPLEMENTATION
HOMEWORK 2
Professor name: Chen, Shang-Liang
Student name: Nguyen Van ThanhStudent ID: P96007019
Class: P9-009 Image Processing &
Software Implementation
Time: [4] 2 b 4
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Contents
Fourier transform
Frequency domain smoothing filters
Sharpening frequency domain filters
Homomorphic filtering
May 8, 2011 2Home work 2
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1. Fouriertransform
May 8, 2011 3
We type the command,
>> f = imread ('Fig4.03(a).jpg');
>> [s, sc, slog] = dft(f);
Home work 2
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2. Frequency domainsmoothingfilters
May 8, 2011 Home work 2 4
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2.1. Ideallow-passfilters (ILPF)
May 8, 2011 Home work 2 5
D0 is a specified distance from the origin of the (centered)
transform.
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2.1. Ideallow-passfilters (ILPF)
May 8, 2011 Home work 2 6
>> f = imread ('Fig4.11(a).jpg');
>> g = ilpf (f, 30);
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2.2. Butterworthlow-passfilter (BLPF)
May 8, 2011 Home work 2 7
With the BLPF, the filter function H (u, v) is,
>> f = imread ('Fig4.11(a).jpg');
>> g = blpf (f, 2, 30);
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2.3. Gaussianlow-passfilter (GLPF)
May 8, 2011 Home work 2 8
>> f = imread ('Fig4.11(a).jpg');
>> g = glpf (f, 30);
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3. Sharpeningfrequency domainfilters
May 8, 2011 Home work 2 9
Image sharpening can be achieved in the frequency domain by
a high-pass filtering process. The high-pass filter function, Hhp
(u, v) is defined as,
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3.1. Idealhigh-passfilters (IHPF)
May 8, 2011 Home work 2 10
>> f = imread ('Fig4.11(a).jpg');
>> g = ihpf (f, 15);
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3.2. Butterworthhigh-passfilters (BHPF)
May 8, 2011 Home work 2 11
>> f = imread ('Fig4.11(a).jpg');
>> g = bhpf (f, 2, 15);
The filter function of the BHPF of order n and with cutoff
frequency locus at distance D0 from the origin is given by,
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3.3. Gaussianhigh-passfilters (GHPF)
May 8, 2011 Home work 2 12
>> f = imread ('Fig4.11(a).jpg');
>> g = ghpf (f, 15);
The filter function of GHPF with cutoff frequency locus at a
distance D0 from the origin is given by,
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4. Homomorphic filtering
May 8, 2011 Home work 2 13
The Homomorphic filtering approach is summarized in the
Figure below.
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4. Homomorphic filtering
May 8, 2011 Home work 2 14
In the Homomorphic filtering, the filter function H (u, v) is
varied according to the special purpose. In the function below,
we choose one, that is,
>> f = imread ('Fig.ex.jpg');
>> g = homo_filter(f,10,0.5,0.2);