National Instruments IMAQ Vision for LabWindows TM /CVI - Manual (Page 45)

Chapter 4 Performing Particle Analysis
© National Instruments Corporation 4-3 IMAQ Vision for LabWindows/CVI User Manual
Removing Unwanted Particles
Use imaqRejectBorder() to remove particles that touch the border of
the image. Reject particles on the border of the image when you suspect
that the information about those particles is incomplete.
Use imaqSizeFilter() to remove large or small particles that do
not interest you. You can also use the IMAQ_ERODE , IMAQ_OPEN , and
IMAQ_POPEN methods in imaqMorphology() to remove small particles.
Unlike imaqSizeFilter() , these three operations alter the size and
shape of the remaining particles.
Use the IMAQ_HITMISS method of imaqMorphology() to locate
particular configurations of pixels, which you define with a structuring
element. Depending on the configuration of the structuring element, the
IMAQ_HITMISS method can locate single isolated pixels, cross-shape or
longitudinal patterns, right angles along the edges of particles, and other
user-specified shapes. Refer to Chapter 9, Binary Morphology, of the
IMAQ Vision Concepts Manual for more information about structuring
elements.
If you know enough about the shape features of the particles you want to
keep, use
imaqParticleFilter2() to filter out particles that do not
interest you.
Separating Touching Particles
Use imaqSeparation() or apply an erosion or an open operation
with imaqMorphology() to separate touching objects. The
imaqSeparation() function is an advanced function that separates
particles without modifying their shapes. However, erosion and open
operations alter the shape of all the particles.
Note A separation is a time-intensive operation compared to an erosion or open operation.
Consider using an erosion or open operation if speed is an issue with your application.
Improving Particle Shapes
Use imaqFillHoles() to fill holes in the particles. Use
imaqMorphology() to perform a variety of operations on the particles.
You can use the IMAQ_AUTOM , IMAQ_CLOSE , IMAQ_PCLOSE , IMAQ_OPEN ,
and IMAQ_POPEN methods to smooth the boundaries of the particles. Open
and proper-open smooth the boundaries of the particle by removing small