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Level Operations (Part 1)
Level Operations (Part 1)
CS 450: Introduction to Digital Signal and Image Processing
Level Operations (Part 1)
Introduction
Point Processing
I
Simplest kind of enhancement: point operations.
Process each point independently of the others.
I
All you can do is remap the sample’s value:
s
=
T
(
r
)
where
I
r
is the value at the point in question
I
s
is the new value in the processed result
I
T
is a
greylevel transformation
or
level operation
Level Operations (Part 1)
Linear Operations
Adding a Constant
Simplest level operation:
s
=
r
+
c
for some constant
c
.
c
>
0
Brighter Image
c
<
0
Darker Image
Level Operations (Part 1)
Linear Operations
Ampliﬁcation (Gain)
Another simple level operation is
ampliﬁcation
(multiplication):
s
=
ar
where
I
r
is the input signal level
I
a
is the ampliﬁcation gain
a
>
1
ampliﬁes the signal (louder/more constrast)
a
<
1
diminishes it (softer/less contrast)
Level Operations (Part 1)
Linear Operations
Linear Level Operators
Linear operators combine gain (multiplication) and offset
(addition):
s
=
ar
+
c
where
I
a
is the gain
I
c
is the offset
Level Operations (Part 1)
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 Fall '09

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