Image Processing Reference
In-Depth Information
Fig. 3.2 Illustration of bilateral filtering for the purpose of detail extraction. a Depicts an original
band of hyperspectral image, b shows the output of the bilateral filter, and c shows the absolute
difference image between a and b .Theimage c has been contrast enhanced for the display purpose
hyperspectral image bands, containing K consecutive bands. We calculate fusion
weights w k (
x
,
y
)
as the following:
I BF
k
|
I k (
x
,
y
)
(
x
,
y
) |+
C
w k (
x
,
y
) =
,
(3.5)
k = 1 ( |
I BF
k
I k (
x
,
y
)
(
x
,
y
) |+
C
)
where I BF is the corresponding filtered band. C is a positive real number which
serves three purposes:
It provides sufficient weightage to the strong edges which are absent in difference
images. The strong edges are least affected by the bilateral filter, and hence their
presence is minimal in the filtered image which acts as the weights. The constant C
provides a constant weightage which acts as the bias along with the actual fusion
weight computed from the bilaterally filtered image.
It brings flexibility to the process by controlling the effect of actual weights w .
When the value of the constant C is very small, its effect on fusion can be practically
neglected. In such case, the actual weights dominate the fusion process, and the
resultant image, thus, purely reflects the strength of the locally dominant features.
On the other hand, when the constant is a significantly large number as compared
to the fusion weights, the fusion becomes an averaging process. Through selection
of an appropriate constant C , the user can adjust the nature of the fused image.
 
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