CAMERAS FRAME GRABBERS IMAGING SOLUTIONS
BOBCAT Hardware User’s Manual
IMPERX
Rev. 2.0.7
6421 Congress Ave.
4/8/2014
Boca Raton, FL 33487
www.imperx.com
+1 (561) 989-0006
203 of 329
3.2.2.1 Single Point Correction
The simplest image enhancement can be achieved by a linear modification of the
original transfer function. If the image brightness is weighted towards a particular
region (dark or bright), this region needs to be suppressed, and the less present (the
flat) region needs to be enhanced. The range of the correction is determined by the
location of the break point (X1, Y1) – Figure 3.4. This point (X1, Y1) divides the
camera transfer function into two regions (two lines). The slope of these lines (the
angle between the X axis and the line) determines the power of the correction. If
the angle is less than 45
O
degrees, the grayscale range will be suppressed. If the
angle is more than 45
O
degrees, the grayscale range will be enhanced. The user can
set the optimum (X1, Y1) values.
Input signal
O
ut
put
s
ignal
O
rig
in
al
T
F
Ne
w T
F
X1
Y1
Figure 3.4 – Single point TF correction.
3.2.2.2 Multi Point Correction
If the image brightness is weighted towards two particular region – dark and
bright, and in the same time mid region has a low dynamic range a multi point
correction will produce much better results compare to the single point correction.
The range of the correction is determined by the location of a pair of the break
point (X1, Y1) and (X2, Y2) – Figure 3.5a. The camera transfer function is divided
into three regions (three lines), which allows multiple grayscale regions to be
corrected independent of each other. If the angle is less than 45
O
degrees, the
grayscale range will be suppressed, if the angle is 45
O
degrees, the gray scale will
not change. If the angle is more than 45
O
degrees, the grayscale range will be
enhanced. The user can set the optimum (X1, Y1) and (X2, Y2) values, note that
X2 > X1. Figure 3.5b shows some of the most typical correction curves. If the
angle in the mid range (between X1 and X2) is negative, the grayscale range will
be reversed. Curve TF 1 enhances the dark image regions and suppresses the bright