National Instruments IMAQTM - Manual (Page 78)

Chapter 5 Performing Machine Vision Tasks
IMAQ Vision for Visual Basic User Manual 5-26 ni.com
• Does not always require the location with sub-pixel accuracy
• Does not require shape information for the region
Complete the following steps to find features in an image using color
location:
1. Define a reference pattern in the form of a template image.
2. Use the reference pattern to train the color location algorithm with
CWIMAQVision.LearnColorPattern .
3. Define an image or an area of an image as the search area. A small
search area reduces the time to find the features.
4. Set CWIMAQMatchColorPatternOptions.FeatureMode to
cwimaqFeatureColorInformation .
5. Set the tolerances and parameters to specify how the method operates
at run time using
CWIMAQMatchColorPatternOptions .
6. Use CWIMAQVision.MatchColorPattern to test the color location
algorithm on test images.
7. Verify the results using a ranking method.
Use CWIMAQVision.WriteImageAndVisionInfo to save the template
image.
Convert Pixel Coordinates to Real-World Coordinates
The measurement points you located with edge detection and pattern
matching are in pixel coordinates. If you need to make measurements using
real-world units, use
CWIMAQVision.ConvertPixelToRealWorldCoordinates to convert
the pixel coordinates into real-world units.
Make Measurements
You can make different types of measurements either directly from the
image or from points that you detect in the image.
Distance Measurements
Use the following methods to make distance measurements for the
inspection application.
Clamp methods measure the separation between two edges in a rectangular
search region. First, clamp methods detect points along the two edges using