Nguyễn Công Phương

DIGITAL IMAGE PROCESSING

Spatial & Frequency Domain Filter  Design

Contents

Introduction to Image Processing & Matlab Image Acquisition, Types, & File I/O Image Arithmetic

Image Transform Spatial & Frequency Domain Filter Design Image Restoration & Blind Deconvolution

Binary Image Processing Image Encryption & Watermarking Image Classification & Segmentation

I. II. III. IV. Affine & Logical Operations, Distortions, & Noise in Images V. VI. VII. VIII. Image Compression IX. Edge Detection X. XI. XII. XIII. Image – Based Object Tracking XIV. Face Recognition XV. Soft Computing in Image Processing

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Spatial & Frequency Domain Filter Design 1. Spatial Domain Filter Design

a) Average/Mean Filter b) Median Filter c) Gaussian Smoothing d) Conservative Smoothing

2. Frequency – Based Filter Design

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Average/Mean Filter

100

105 104

110

150 101

1 9

102

103 104

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Median Filter

• The median is calculated by first sorting all the elements in numerical order and then taking the middle one.

• If the number of elements is even, the average

of the two middle elements is used.

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Spatial & Frequency Domain Filter Design 1. Spatial Domain Filter Design

a) Average/Mean Filter b) Median Filter c) Gaussian Smoothing d) Conservative Smoothing

2. Frequency – Based Filter Design

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Gaussian Smoothing

2

2

(

)

m m  0

n n 0

) (   2 2 

e

h m n , )

(

1 2 2 

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Conservative Smoothing

• Conservative: not modifying the pixel blindly. • Algorithm:

1. A = min(neighborhood); 2. B = max(neighborhood); 3. Central pixel = • A, if cp < A, • B, if cp > B, • Else no change.

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Spatial & Frequency Domain Filter Design 1. Spatial Domain Filter Design

a) Average/Mean Filter b) Median Filter c) Gaussian Smoothing d) Conservative Smoothing

2. Frequency – Based Filter Design

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Frequency – Based Filter Design

FFT

IFFT

Image Image

Filter Filter

Image Image

Image in  Image in  frequency  frequency  domain domain

Image in  Image in  frequency  frequency  domain domain

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