IEG4160_Part3 - IEG 4160: Image and Video Processing....

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IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu Image Enhancement in Spatial Domain Background Basic gray level transformation Histogram processing ± Histogram equalization Arithmetic and logic operations Spatial filtering ± Smoothing ± Sharpening Combining methods Conclusions
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Page 2 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Background Spatial domain ± Aggregate of pixels in an image Spatial domain processes ± ± T : operator; f : input; g : output Neighborhood about ( x , y ) ± A subimage area centered at ( x , y ) (, ) [ (, ) ] g x y T f x y = 1 , . . . , (, ) ] n g x y T f x yf x y =
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Page 3 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Background The simplest form of T ± when the neighborhood is of size Gray-level transform ± r : input gray level; s : output gray level 11 × () s Tr = Contrast stretching Thresholding
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Page 4 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Lookup table implementation example: () s Tr = T maps a pixel value r into a pixel value s int T[256], Input[128][128], Output[128][128]; // Designing a lookup table for(i=0; i<100; ++i) T[i]=0; for(i=100; i<255; ++i) T[i]=255; // Gray level transformation for(i=0; i<128; ++i) for(j=0; j<128; ++j) Output[i][j]=T[Input[i][j]]; 0 255 100 255 100 C code A = imread(‘img.bmp','bmp'); B = A>=100; Matlab code
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Page 5 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Linear ± Identity ± Negative Logarithmic ± Log ± Inverse-log Power-law ± n th power ± n th root
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Page 6 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Image negatives 1 s Lr = −− Original image Negative image
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Page 7 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Log transformation log(1 ) s cr = +
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Page 8 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Log transformation: an example Original spectrum image s r 0 255 6 1.5 10 × s’ r 0 6.2 6 1.5 10 × s 0 255 s’ 6.2 Enhanced image
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Page 9 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Power-law transformation s cr γ = c = 1
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Page 10 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Power-law transformation ± Gamma correction Gamma: 1.8—2.5
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Page 11 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Power-law transformation ± Another example Original image s r γ = 3.0 γ= 5.0 4.0
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Page 12 IEG 4160: Image and Video Processing. Lecturer: Jianzhuang Liu 3. Image Enhancement in Spatial Domain Basic gray level transformation Piecewise linear transformation functions ± Contrast stretching ± Gray-level slicing Contrast stretching Gray-level slicing
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This note was uploaded on 10/13/2009 for the course CS 5150 taught by Professor Xulei during the Spring '09 term at University of Central Arkansas.

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IEG4160_Part3 - IEG 4160: Image and Video Processing....

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