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If all the objects in your grayscale image are either brighter or darker than 
your background, you can use 

imaqAutoThreshold()

 to automatically 

determine the optimal threshold range and threshold your image. 
Automatic thresholding techniques offer more flexibility than simple 
thresholds based on fixed ranges. Because automatic thresholding 
techniques determine the threshold level according to the image histogram, 
the operation is more independent of changes in the overall brightness and 
contrast of the image than a fixed threshold. These techniques are more 
resistant to changes in lighting, which makes them well suited for 
automated inspection tasks.

If your grayscale image contains objects that have multiple discontinuous 
grayscale values, use 

imaqMultithreshold()

 to specify multiple 

threshold ranges.

If you need to threshold a color image, use 

imaqColorThreshold()

. 

You  must specify threshold ranges for each of the color planes using either 
the RGB or HSL color model. The binary image resulting from a color 
threshold is an 8-bit binary image.

After you threshold your image, you may want to improve the resulting 
binary image with binary morphology. You can use primary binary 
morphology or advanced binary morphology to remove unwanted 
particles, separate connected particles, or improve the shape of particles. 
Primary morphology functions work on the image as a whole by processing 
pixels individually. Advanced morphology operations are built upon the 
primary morphological operators and work on particles as opposed to 
pixels. Refer to Chapter 9, Binary Morphology, of the IMAQ Vision 
Concepts Manual for lists of which morphology functions are primary 
and which are advanced.

The advanced morphology functions require that you specify the type of 

 to use. Use 

 when you want IMAQ Vision to 

consider pixels to be part of the same particle only when the pixels touch 
along an adjacent edge. Use 

 when you want IMAQ Vision 

to consider pixels to be part of the same particle even if the pixels touch 
only at a corner. Refer to Chapter 9, Binary Morphology, of the 
IMAQ Vision Concepts Manual for more information about connectivity.

Use the same type of connectivity throughout your application.