Chapter 5
Performing Machine Vision Tasks
©
National Instruments Corporation
5-15
IMAQ Vision for LabWindows/CVI User Manual
Positional Information
A template with strong edges in both the x and y directions is easier to
locate. Figure 5-9a shows good positional information in both the x and
y directions, while Figure 5-9b shows insufficient positional information in
the y direction.
Figure 5-9.
Positional Information
Background Information
Unique background information in a template improves search
performance and accuracy. Figure 5-10a shows a pattern with insufficient
background information. Figure 5-10b illustrates a pattern with sufficient
background information.
Figure 5-10.
Background Information
Training the Pattern Matching Algorithm
After you create a good template image, the pattern matching
algorithm has to learn the important features of the template. Use
imaqLearnPattern2()
to learn the template. The learning process
depends on the type of matching that you expect to perform. If you do not
expect the instance of the template in the image to rotate or change its size,
then the pattern matching algorithm has to learn only those features from
a.
b.
a.
b.
