National Instruments IMAQ Vision for LabWindows TM /CVI - Manual (Page 46)

Chapter 4 Performing Particle Analysis
IMAQ Vision for LabWindows/CVI User Manual 4-4 ni.com
isthmuses while close widens the isthmuses. Close and proper-close fill
small holes in the particle. Auto-median removes isthmuses and fills holes.
Refer to Chapter 9, Binary Morphology, of the IMAQ Vision Concepts
Manual for more information about these methods.
Make Particle Measurements
After you create a binary image and improve it, you can make particle
measurements. IMAQ Vision can return the measurements in uncalibrated
pixels or calibrated real-world units. With these measurements you can
determine the location of particles and their shape features. Use the
following functions to perform particle measurements:
• imaqCountParticles() —This function returns the number of
particles in an image and calculates various measurements for each
particle.
• imaqMeasureParticle() —This function uses the calculations
from imaqCountParticles() to return specific measurements of
a particle.
Table 4-1 lists all of the measurements that imaqMeasureParticle()
returns.
Table 4-1. Particle Measurements
Measurement Description
IMAQ_MT_AREA Area of the particle
IMAQ_MT_AREA_BY_IMAGE_AREA Percentage of the particle area
covering the image area
IMAQ_MT_AREA_BY_PARTICLE_AND_HOLES_AREA Percentage of the particle area in
relation to the area of its particle and
holes
IMAQ_MT_AVERAGE_HORIZ_SEGMENT_LENGTH Average length of a horizontal
segment in the particle
IMAQ_MT_AVERAGE_VERT_SEGMENT_LENGTH Average length of a vertical segment
in the particle
IMAQ_MT_BOUNDING_RECT_BOTTOM Y-coordinate of the lowest particle
point
IMAQ_MT_BOUNDING_RECT_TOP Y-coordinate of the highest particle
point