2.6 Filter Design ............................................................................ 33

2.7
Summary ................................................................................. 36

Problems ............................................................................................. 36

Chapter 3 Image Filtering, Enhancement, and Restoration ................................ 39

3.1 Introduction and Overview...................................................... 39

3.2 Point Processing ......................................................................40

3.2.1 Contrast Enhancement ............................................... 41

3.2.2 Bit-Level Slicing ......................................................... 43

3.2.3 Histogram Equalization .............................................44

3.3 Mask Processing: Linear Filtering in Space Domain ............. 47

3.3.1 Low-Pass Filters .........................................................48

3.3.2 Median Filters ............................................................ 50

3.3.3 Sharpening Spatial Filters .......................................... 53

3.3.3.1
High-Pass Filters ......................................... 53

3.3.3.2 High-Boost Filters ...................................... 54

3.3.3.3 Derivative Filters ........................................ 56

3.4 Frequency-Domain Filtering ................................................... 58

3.4.1 Smoothing Filters in Frequency Domain ................... 59

3.4.1.1 Ideal Low-Pass Filter .................................. 59

3.4.1.2 Butterworth Low-Pass Filters .....................60

3.4.2 Sharpening Filters in Frequency Domain ..................60

3.4.2.1 Ideal High-Pass Filters ................................60

3.4.2.2 Butterworth High-Pass Filters .................... 61

3.5 Summary ................................................................................. 61

Problems............................................................................................. 61

Reference ............................................................................................ 62

Chapter 4 Edge Detection and Segmentation of Images .................................... 63

4.1 Introduction and Overview...................................................... 63

4.2 Edge Detection ........................................................................ 63

4.2.1 Sobel Edge Detection ................................................. 63

4.2.2 Laplacian of Gaussian Edge Detection ......................66

4.2.3 Canny Edge Detection ................................................ 67

4.3 Image Segmentation ................................................................ 69

4.3.1 Point Detection ........................................................... 70

4.3.2 Line Detection ............................................................ 71

4.3.3 Region and Object Segmentation ............................... 72

4.3.3.1 Region Segmentation Using
Luminance Thresholding............................ 73

4.3.3.2 Region Growing .......................................... 75

4.3.3.3
Quad-Trees .................................................. 76

4.4 Summary ................................................................................. 77

Problems ............................................................................................. 77

viii
Contents