l2 - CMPEN/EE455 Lect 2 4 Spatial Coverage of Digital Image...

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1 CMPEN/EE455 Lecture 2 Elements of Human Perception (continued) Perceived brightness and contrast Electromagnetic spectrum (G&W Figure 2.10) - “Eagle Eye” demo Read Sections 2.1-2.2 of G&W
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CMPEN/EE455 – Lect 2 2 DIGITAL IMAGES - mathematical representation f image ( x,y ) image coordinates, space domain pixel, pel, picture element f ( x,y ) brightness (gray level) of pixel ( x,y ) [0 , L max ] gray scale: range of allowed gray levels L max = 255 usually; i.e., we usually use an 8-bit gray scale, 0 f ( x,y ) 255 f ( x,y ) 0 x N - 1 and 0 y N - 1 N × N digital image
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CMPEN/EE455 – Lect 2 3 digital image N × N array of pixels with associated gray-scale (gray-level) values: { f ( x,y ) } = f (0 , 0) f (0 , 1) f (0 , 2) ... f (0 ,N - 1) f (1 , 0) f (1 , 1) ... ... f (1 ,N - 1) . . . . . . ... ... . . . f ( N - 2 , 0) . . . ... ... . . . f ( N - 1 , 0) f ( N - 1 , 1) ... ... f ( N - 1 ,N - 1)
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Unformatted text preview: CMPEN/EE455 Lect 2 4 Spatial Coverage of Digital Image f ( i,j ) gray level of ( i,j ) th pixel CMPEN/EE455 Lect 2 5 Also, quantize gray scale [0 ,L max ]: G = 2 m number of gray levels m = 8 bits G = 2 m = 256 { , 1 , 2 , ..., 255 } most common! 1 byte per pixel G = L max G-1 = gray-scale quantization interval CMPEN/EE455 Lect 2 6 Memory for Digital Image N N m bits N N bytes (8-bit gray scale) e.g.) N = 256 m = 8- Memory usage grows fast! digital image resolution determined by: N grid size spatial sampling interval m # of gray levels...
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This note was uploaded on 09/24/2009 for the course EE 455 taught by Professor Staff during the Fall '08 term at Pennsylvania State University, University Park.

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l2 - CMPEN/EE455 Lect 2 4 Spatial Coverage of Digital Image...

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