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
