052600 VU Signal and Image Processing Image Enhancement Torsten Möller + Hrvoje Bogunović + Raphael Sahann torsten.moeller@univie.ac.at hrvoje.bogunovic@meduniwien.ac.at raphael.sahann@univie.ac.at vda.cs.univie.ac.at/teaching/sip/17s/ Raphael 1 Sahann
Overview Image Enhancement Basic Transformation Functions Histogram Processing Spatial Filtering 2
Basic Transformations Gonzalez & Woods - Digital Image Processing (3rd Edition) 3
Intensity Transformations Gonzalez & Woods - Digital Image Processing (3rd Edition) 4
Negative Transformation Gonzalez & Woods - Digital Image Processing (3rd Edition) 5
Log Transformation Gonzalez & Woods - Digital Image Processing (3rd Edition) 6
Power-Law (Gamma) Transformations Gonzalez & Woods - Digital Image Processing (3rd Edition) 7
Gamma Correction Gonzalez & Woods - Digital Image Processing (3rd Edition) 8
Gamma Correction Gonzalez & Woods - Digital Image Processing (3rd Edition) 9
Gamma Correction Gonzalez & Woods - Digital Image Processing (3rd Edition) 10
Contrast Stretching 11
Intensity Level Slicing Gonzalez & Woods - Digital Image Processing (3rd Edition) 12
Intensity Level Slicing Gonzalez & Woods - Digital Image Processing (3rd Edition) 13
Overview Image Enhancement Basic Transformation Functions Histogram Processing Spatial Filtering 14
Histogram Processing Gonzalez & Woods - Digital Image Processing (3rd Edition) 15
Histogram Processing Gonzalez & Woods - Digital Image Processing (3rd Edition) 16
Probability Density Function Gonzalez & Woods - Digital Image Processing (3rd Edition) 17
Histogram Equalization kx s k = T (r k )=(L 1) p r (r j ) j=0 kx (L 1) = MN n j k =0, 1, 2,...,L 1 j=0 18
Histogram Equalization kx s k = T (r k )=(L 1) p r (r j ) Example: 3-bit image (L = 8) of size 64 x 64 pixels (MN = 4096) with intensity levels shown in table: j=0 19
Histogram Equalization kx s k = T (r k )=(L 1) p r (r j ) Example: 3-bit image (L = 8) of size 64 x 64 pixels (MN = 4096) with intensity levels shown in table: j=0 s0 = 1.33 1 s1 = 3.08 3 s2 = 4.55 5 s3 = 5.67 6 s4 = 6.23 6 s5 = 6.65 7 s6 = 6.86 7 s7 = 7.00 7 20
Histogram Equalization s0 = 1.33 1 s1 = 3.08 3 s2 = 4.55 5 s3 = 5.67 6 s4 = 6.23 6 s5 = 6.65 7 s6 = 6.86 7 s7 = 7.00 7 Gonzalez & Woods - Digital Image Processing (3rd Edition) 21
Histogram Equalization Gonzalez & Woods - Digital Image Processing (3rd Edition) 22
Histogram Equalization Gonzalez & Woods - Digital Image Processing (3rd Edition) 23
Histogram Equalization Gonzalez & Woods - Digital Image Processing (3rd Edition) 24
Histogram Specification Gonzalez & Woods - Digital Image Processing (3rd Edition) 25
Histogram Specification Gonzalez & Woods - Digital Image Processing (3rd Edition) 26
Histogram Specification Gonzalez & Woods - Digital Image Processing (3rd Edition) 27
Histogram Specification Gonzalez & Woods - Digital Image Processing (3rd Edition) 28
Local Histogram Statistics Gonzalez & Woods - Digital Image Processing (3rd Edition) 29
Overview Image Enhancement Basic Transformation Functions Histogram Processing Spatial Filtering 30
Linear Spatial Filtering Gonzalez & Woods - Digital Image Processing (3rd Edition) 31
Smoothing Filter Gonzalez & Woods - Digital Image Processing (3rd Edition) 32
Smoothing Filter Gonzalez & Woods - Digital Image Processing (3rd Edition) 33
Smoothing Filter - Application Gonzalez & Woods - Digital Image Processing (3rd Edition) 34
Median Filter Gonzalez & Woods - Digital Image Processing (3rd Edition) 35
Non-Local Means Denoising Even better results for noise reduction Looks at similar regions of the image to reconstruct current region Publication and Demo: http://www.ipol.im/pub/art/2011/bcm_nlm/ 36
Laplacian Image Sharpening (Second Derivative) Gonzalez & Woods - Digital Image Processing (3rd Edition) 37
Laplacian Sharpening Gonzalez & Woods - Digital Image Processing (3rd Edition) 38
Unsharp Masking and Highboost Filtering Gonzalez & Woods - Digital Image Processing (3rd Edition) 39
Gradient Filter Gonzalez & Woods - Digital Image Processing (3rd Edition) 40
Combining Enhancement Methods Gonzalez & Woods - Digital Image Processing (3rd Edition) 41
Combining Enhancement Methods Gonzalez & Woods - Digital Image Processing (3rd Edition) 42