National Instruments IMAQ Vision for Measurement Studio - Manual (Page 71)

Chapter 5 Machine Vision
© National Instruments Corporation 5-25 IMAQ Vision for LabWindows/CVI User Manual
reference pattern in all cases, you have selected a good template.
Otherwise, refine the current template, or select a better template until both
training and testing are successful.
Finding Points Using Color Location
Color location algorithms provide a quick way to locate regions in an image
with specific colors.
Use color location when your application:
• Requires the location and the number of regions in an image with their
specific color information
• Relies on the cumulative color information in the region, instead of the
color arrangement in the region
• Does not require the orientation of the region
• Does not always require the location with sub-pixel accuracy
• Does not require shape information for the region
Follow these general 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
imaqLearnColorPattern() .
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 the featureMode element of the imaqMatchColorPattern()
options parameter to IMAQ_COLOR_FEATURES .
5. Set the tolerances and parameters to specify how the algorithm
operates at run time using the options parameter of
imaqMatchColorPattern() .
6. Test the color location algorithm on test images using
imaqMatchColorPattern() .
7. Verify the results using a ranking method.
You can save the template image using imaqWriteVisionFile() .