Point Processing (Szeliski 3.1)
cs129: Computational PhotographyJames Hays, Brown, Fall 2012Some figures from Alexei Efros,
Steve Seitz, and Gonzalez et al.
Image Processing
image filtering: change range of imageg(x) = h(f(x))
f
x
hf
x
f
x
hf
x
image warping: change domain of imageg(x) = f(h(x))
Image Processing
h
h
f
f g
g
image filtering: change range of image
g(x) = h(f(x))
image warping: change domain of imageg(x) = f(h(x))
Point Processing
The simplest kind of range transformations are these independent of position x,y:
g = t(f)
This is called point processing.
What can they do?
What’s the form of t?
Important: every pixel for himself – spatial information completely lost!
For example: Gamma “correction”
Is an instance of these power law intensity transformations.
Typically, gamma = 2.2 for a display device, and 1/2.2 for encoding.
The result is a more perceptually uniform encoding.