Image Enhancement - Nubacad.com

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Cumulative Histogram Records the cumulative frequency distribution of gray levels in an image. k nk sk = T ( r) = ∑ n j= 0 The cumulative frequency of a gray level, i, is the number of times that a gray level less than or equal to i occurs in an image. May 07, 2011 Dr. Al-Amin http://www.geocities.<strong>com</strong>/alamin_bhuiyan 12
Histogram Equalization Redistribution of gray levels: an attempt to flatten the frequency distribution. The probability of occurrence of gray level r k , p r (r k ) = n k /n, for k = 0,1,…, L-1; where n is the total number of pixels, r k is the k-th gray level and n k is the number of pixels having gray level r k . Then the Histogram Equalization or Histogram Linearization transformation function: k k n j sk = T ( rk ) = ∑ pr ( rj ) = ∑ ; n j= 0 j= 0 for k = 0,1,2,..,L-1 The function s can be considered as cumulative sum of p r (r k ) More gray levels are allocated where there are most pixels, fewer gray levels where there fewer pixels. This tends to increase contrast in the most heavily populated regions of the histogram. May 07, 2011 Dr. Al-Amin http://www.geocities.<strong>com</strong>/alamin_bhuiyan 13
Page 1 and 2: Image Enhancement Modify color or g
Page 3 and 4: Gray Level Transformation Function:
Page 5 and 6: Image Negatives • s = T(r) = L-1-
Page 7 and 8: Piece-wise Linear Gray-level Transf
Page 9 and 10: Gray-level Slicing Provides a binar
Page 11: Histogram • The histogram of an i
Page 15 and 16: Histogram Equalization … May 07,
Page 17 and 18: Enhancing using Arithmetic/Logic Op
Page 19 and 20: Image Subtraction Subtraction of tw

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