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Digital Image Processing
Image Enhancement Spatial Filtering
21/11/15 Duong Anh Duc - Digital Image Processing 1
Image Enhancement: Spatial Filtering
Image enhancement in the spatial domain can be represented as:
Transformation
Enhanced Image
g(m,n) = T(f)(m,n)
Given Image
The transformation T maybe linear or nonlinear. We will mainly study linear operators T but will see one important nonlinear operation.
21/11/15 Duong Anh Duc - Digital Image Processing 2
How to specify T
If the operator T is linear and shift invariant (LSI), characterized by the point-spread sequence (PSS) h(m,n) , then
(recall
21/11/15
convolution)
Duong Anh Duc - Digital Image Processing 3
How to specify T
In practice, to reduce computations, h(m,n) is of “finite extent:
h(k,l) = 0 for (k,l)
where is also called
a small set (called neighborhood). is as the support of h.
In the frequency domain, this can be represented as:
G(u,v) = He(u,v) Fe(u,v)
where He(u,v) and Fe(u,v) are obtained after appropriate zeropadding.
21/11/15 Duong Anh Duc - Digital Image Processing 4
How to specify T
Many LSI operations can be interpreted in the frequency domain as a “filtering operation.” It has the effect of filtering frequency components (passing certain frequency components and stopping others).
The term filtering is generally associated with such operations.
21/11/15 Duong Anh Duc - Digital Image Processing 5
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