EECE253_03_PointProcessing

EECE253_03_PointProcessing - EECE/CS 253 Image Processing...

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EECE/CS 253 Image Processing Richard Alan Peters II Department of Electrical Engineering and Computer Science Fall Semester 2011 Lecture Notes: Lecture Notes: The Point Processing of Images This work is licensed under the Creative Commons Attribution-Noncommercial 2.5 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA.
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12/06/11 2 2000-2011 Richard Alan Peters II Point Processing of Images In a digital image, point = pixel. Point processing transforms a pixel’s value as function of its value alone; it does not depend on the values of the pixel’s neighbors. In a digital image, point = pixel. Point processing transforms a pixel’s value as function of its value alone; it does not depend on the values of the pixel’s neighbors.
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12/06/11 3 2000-2011 Richard Alan Peters II Brightness and contrast adjustment Gamma correction Histogram equalization Histogram matching Color correction. Brightness and contrast adjustment Gamma correction Histogram equalization Histogram matching Color correction. Point Processing of Images
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12/06/11 4 2000-2011 Richard Alan Peters II Point Processing Point Processing original + gamma - gamma + brightness - brightness original + contrast - contrast histogram EQ histogram mod
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12/06/11 5 2000-2011 Richard Alan Peters II Let I be a 1-band (grayscale) image. I ( r , c ) is an 8-bit integer between 0 and 255. Histogram, h I , of I : a 256-element array, h I h I ( g ), for g = 1, 2, 3, …, 256, is an integer h I ( g ) = number of pixels in I that have value g -1. Let I be a 1-band (grayscale) image. I ( r , c ) is an 8-bit integer between 0 and 255. Histogram, h I , of I : a 256-element array, h I h I ( g ), for g = 1, 2, 3, …, 256, is an integer h I ( g ) = number of pixels in I that have value g -1. The Histogram of a Grayscale Image
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12/06/11 6 2000-2011 Richard Alan Peters II The Histogram of a Grayscale Image 16-level (4-bit) image b l a c k m a r k s p i x e l s w i t h i n t e n s i t y g lower RHC: number of pixels with intensity g
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12/06/11 7 2000-2011 Richard Alan Peters II The Histogram of a Grayscale Image Plot of histogram: number of pixels with intensity g Black marks pixels with intensity g
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12/06/11 8 2000-2011 Richard Alan Peters II The Histogram of a Grayscale Image Plot of histogram: number of pixels with intensity g Black marks pixels with intensity g
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12/06/11 9 2000-2011 Richard Alan Peters II ( ) 1 the number of pixels in with graylevel . h g g + = I I Luminosity The Histogram of a Grayscale Image
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12/06/11 10 2000-2011 Richard Alan Peters II If I is a 3-band image (truecolor, 24-bit) then I ( r , c,b ) is an integer between 0 and 255. Either I has 3 histograms: h R ( g +1) = # of pixels in I (:,:,1) with intensity value g h G ( g +1) = # of pixels in I (:,:,2) with intensity value g h B ( g +1) = # of pixels in I (:,:,3) with intensity value g or 1 vector-valued histogram, h ( g, 1 ,b ) where h ( g +1 , 1 , 1) = # of pixels in I with red intensity value g h ( g +1 , 1 , 2) = # of pixels in I with green intensity value g h ( g
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