L5+Notes

L5+Notes - Barrett - CS450 Winter 2011 Lecture 5 Level...

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Barrett - CS450 Winter 2011 Lecture 5 Level (Point) Operations Objectives : To understand how Level (Point) Operations, Offset, Gain, and simple grayscale transformations (look-up tables) affect images. 1. Gain and Offset Gain =1, Offset = 0 Gain =1, Offset = 64 Gain =1, Offset = -64 Gain =-1, Offset = 256 Gain =2, Offset = -128 Gain = , Offset = - Nonlinear Gain, Zero Offset Nonlinear Gain, Zero Offset
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Barrett - CS450 Winter 2011 2. Grayscale Transformation – Level Operations – Look-up Tables 3. Histogram Stretching (not to be confused with Histogram Equalization) Histogram Stretching – linear stretch to fill the dynamic range Histogram Equalization – nonlinear stretch What happens to the resulting histogram? Can we manufacture pixel values? What happens to the values that get mapped to < 0? > 0? They get clipped at 0 and 255? How do we get them back? (We don’t) What does this suggest about how we acquire images? (bracket) In general, what does histogram stretching accomplish? (Increases/enhances contrast)
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L5+Notes - Barrett - CS450 Winter 2011 Lecture 5 Level...

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