Rockwell Automation 5370-CVIM2 Module - Manual (Page 314)

Chapter 7
Inspection Tools
7–76
Contrast field depends on the placement of the user–selectable coefficients
within the kernel.
When active, the Contrast field enables you to select a contrast value of 1, 2,
3, or 4, according to the kernel selection. The contrast function has the effect
of enhancing the gradients (edges).
In particular, a contrast setting of “1” will “double” the gray scale value of
each pixel; a contrast setting of “2” will double the value again; and so on,
with the following restrictions: Pixels in unsigned images whose “doubled”
gray scale values exceed 255 are “clipped” to a maximum value of 255, while
pixels in signed images whose doubled gray scale values exceed +127 are
clipped to a maximum value of 127, and values below –128 are clipped to
–128.
When you pick the Contrast field, the Contrast selection panel appears, as
shown in Figure 7.64.
Figure 7.64 (A), (B), and (C) illustrate using a Sobel X kernel and the Sign
LUT. In (A), the selected contrast value is 0 (default); in (B), the contrast
value is 1; and in (C), the contrast value is 2.
Figure 7.64 Example: Effects of Contrast Adjustments
B A
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C
Notice that the vertical gradients on the round objects in the three images are
more pronounced with each increase in the contrast value.