
where a is an adjustable parameter. This image intensity scaling is usually used
for contrast stretching, clipping, display calibration, etc.
6.2.2 Clipping and Thresholding
Image clipping is a special case of contrast stretching that is useful in noise
reduction when the input image, f, is known to lie in the range of 0 to L.
The transform is defined in the equation
g ¼
00# f < a
aIa# f < b
Lf$ b
8
<
:
(6:4)
where a and b are usually obtained from the histogram of the image and they
specify the valley between the peaks of the histogram (see Fig. 6.1). When a ¼ b,
the transform is called thresholding, and the output is a binary image.
6.2.3 Image Subtraction ...