EECE253_10_PixelizationQuantization

EECE253_10_PixelizationQuantization - EECE\CS 253 Image...

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EECE\CS 253 Image Processing Richard Alan Peters II Department of Electrical Engineering and Computer Science Fall Semester 2007 Lecture Notes Lecture Notes: Pixelization and Quantization 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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27 April 2008 2 27 April 2008 2 1999-2007 by Richard Alan Peters II Pixelization … … is a special effect often used to hide identities …
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27 April 2008 3 27 April 2008 3 1999-2007 by Richard Alan Peters II Pixelization … or to “clean up” an image.
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27 April 2008 4 27 April 2008 4 1999-2007 by Richard Alan Peters II Pixelization and Quantization pixelated high-res image quantized pixelated & quantized
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27 April 2008 5 27 April 2008 5 1999-2007 by Richard Alan Peters II Pixelization and Quantization pixel grid column index column index row index pixelated high-res image quantized pixelated & quantized
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27 April 2008 6 27 April 2008 6 1999-2007 by Richard Alan Peters II Pixelization ) , ( I c r P ( ) χ ρ , I high-res image pixelated image Take the average within each square. Take the average within each square. ( ) ( ) ( ) ( ) Δ = Δ = ∑∑ Δ + Δ = Δ + Δ = DS P 1 11 1 2 DS I I ; , I 1 , I ρχ r r c c c r ( upsampled )
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27 April 2008 7 27 April 2008 7 1999-2007 by Richard Alan Peters II Take the average within each square. Take the average within each square. ) , ( I c r P ( ) χ ρ , I high-res image pixelated image Pixelization ( ) ( ) ( ) ( ) Δ = Δ = ∑∑ Δ + Δ = Δ + Δ = DS P 1 11 1 2 DS I I ; , I 1 , I ρχ r r c c c r ( upsampled )
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27 April 2008 8 27 April 2008 8 1999-2007 by Richard Alan Peters II Take the average within each square. Take the average within each square. ) , ( I c r P ( ) χ ρ , I high-res image pixelated image Pixelization ( ) ( ) ( ) ( ) Δ = Δ = ∑∑ Δ + Δ = Δ + Δ = DS P 1 11 1 2 DS I I ; , I 1 , I ρχ r r c c c r ( upsampled )
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27 April 2008 9 27 April 2008 9 1999-2007 by Richard Alan Peters II Take the average within each square. Take the average within each square. ) , ( I c r P ( ) χ ρ , I high-res image pixelated image Pixelization ( ) ( ) ( ) ( ) Δ = Δ = ∑∑ Δ + Δ = Δ + Δ = DS P 1 11 1 2 DS I I ; , I 1 , I ρχ r r c c c r ( upsampled )
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27 April 2008 10 27 April 2008 10 1999-2007 by Richard Alan Peters II Pixelization Procedure (Part 1) ( ) ( ) ( ) ( ) {} , , , I mean , , I , , DS b b c r c r χ ρ N = ( ) ( ) ( ) ( ) . 1 1 , , 1 , , 1 1 , , 1 , , , + + + + = s c cs cs s r rs rs c r N To pixelize an R × C × B image I by a factor, s : Let I DS be an R / s × C / s × B image. Let the value of I DS at location ( r , c , b ) be the average value of I in the s -square neighborhood starting at ( rs , cs , b ). where
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27 April 2008 11 27 April 2008 11 1999-2007 by Richard Alan Peters II Pixelization Procedure (Part 2) ( ) ( ) ( ) ( ) . , , for , , I , , I DS P c r b c r b N = χ ρ ( ) ( ) ( ) {} ( ) . 1 1 , , 1 , , 1 1 , , 1 , , , + + + + = s c cs cs s r rs rs c r N Let I P be an R × C × B image.
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EECE253_10_PixelizationQuantization - EECE\CS 253 Image...

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