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National Instruments IMAQ Vision for Measurement Studio Make Particle Measurements

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Chapter4 BlobAnalysis

IMAQVision for LabWindows/CVI User Manual 4-4 ni.com

Ifyou know enough about the shape features of the blobs you want to keep,

use imaqParticleFilter()to filter out particles that do not interest

you.If you do not have enough information about the particles you want to

keepat this point in your processing, usethe particle measurement

functionsto obtain this information before applying a particle filter. See the

Make Particle Measurements section for more information about the

measurement functions.

Separating TouchingBlobs

Use imaqSeparation()or apply an erosion or an open ope ration with

imaqMorphology()to separate touchi ng objects. The

imaqSeparation()function is an advanced function that separates blobs

withoutmodifying their shapes. However, e rosion and open functions alter

the shape of all the blobs.

Note Aseparation is a time-intensive operation compared to an erosion or open operation.

Considerusing an erosion or open if speed is an issue with your application.

Improving Blob Shapes

Use imaqFillHoles()to fill hol es in the blobs. Use

imaqMorphology()to perform a variety of operations on t he blobs. You

canuse t he IMAQ_AUTOM,IMAQ_CLOSE,IMAQ_PCLOSE,IMAQ_OPEN,and

IMAQ_POPENmethods to smooth the boundaries of the blobs. Open and

proper open smooth the boundaries of the blob by removing small

isthmuses while close widens the isthmuses. Close and proper close fill

smallholes in the blob. Auto-median removes isthmuses and fills holes.

For more information about these methods, see Chapter 9, Binary

Morphology,intheIMAQ Visio n Concepts Manual.

Make Particle Measurements

Afteryou create a binary image and improve it, you can make particle

measurements.With these measurements you can determine the location of

blobsand their shape features. Use the following functions to perform

particle measurements:

•imaqGetParticleInfo()—Thisfunction returns the number of

blobs in an image and a report containing the pixel area, real-world

area, and bounding rectangle of the blobs. Youcan use the bounding

rectangle to determine the location of theblob in the image. You can

also havethis function return a report con taining 16 of the most

Contents

Main IMAQ Page Important Information Warranty Copyright Trademarks WARNINGREGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS Conventions Contents Chapter 1 Introduction to IMAQ Vision Chapter 2 Getting Measurement-Ready Images Chapter 3 Grayscale and Color Measurements Chapter 4 Blob Analysis Chapter 5 Machine Vision Page Introduction to IMAQ Vision About IMAQ Vision Documentation and Examples Application Development Environments IMAQ Vision Function Tree Page IMAQ Machine Vision Function Tree Creating IMAQ Vision Applications Chapter1 Introductionto IMAQ Vision Figure1-2. InspectionSteps for Building a Vision Application IMAQVision for LabWindows/CVI User Manual 1-6 ni.com Getting Measurement-Ready Images Set Up Your Imaging System Calibrate Your Imaging System Create an Image Page Source and Destination Images AcquireorReadanImage Acquiring an Image Reading a File Converting an Array to an Image Display an Image Attach Calibration Information Analyze an Image Improve an Image Lookup Tables Filters Convolution Filter Nth Order Filter Grayscale Morphology FFT Page Complex Image Operations Grayscale and Color Measurements Define Regions of Interest Interactively Defining Regions Page Page Page Page Programmatically Defining Regions Defining Regions with Masks Measure Grayscale Statistics Measure Color Statistics Figure3-4. Primary Components of a Color Image Comparing Colors Learning Color Information Choosing the Right Color Information Specifying the Color Information to Learn Using the Entire Image Using a Region in the Image Using Multiple Regions in the Image Choosing a Color Representation Sensitivity Ignoring Learned Colors Blob Analysis Correct Image Distortion Create a Binary Image Improve the Binary Image Removing Unwanted Blobs Separating TouchingBlobs Improving Blob Shapes Make Particle Measurements Page Page Convert Pixel Coordinates to Real-World Coordinates Machine Vision Locate Objects to Inspect UsingEdgeDetectiontoBuildaCoordinateTransform Page Using Pattern Matching to Build a Coordinate Transform Page Chapter5 MachineVision NationalInstruments Corporation 5-7 IMAQVision for LabWindows/CVI User Manual ChoosingaMethodtoBuildtheCoordinateTransform Figure5-4. Buildinga Coordinate Transform Set Search Areas Interactively Defining Regions Programmatically Defining Regions Find Measurement Points Finding Features Using Edge Detection Finding Lines or Circles Figure5-5. Findinga Straight Feature Finding Edge Points Along One Search Contour Finding Edge Points Along Multiple Search Contours Finding Points Using Pattern Matching Defining and Create Good TemplateImages Symmetry Feature detail Positional information Background information Trainingthe Pattern Matching Algorithm Defining a Search Area Setting Matching Parameters and Tolerances Match Mode Minimum Contrast Rotation Angle Ranges Testingthe Search Algorithm on Test Images Using a Ranking Method to Verify Results Finding Points Using Color Pattern Matching Defining and Creating Good Color TemplateImages Color Information Symmetry Feature Detail Positional Information Trainingthe Color Pattern Matching Algorithm Defining a Search Area Setting Matching Parameters and Tolerances Color Sensitivity Search Strategy Color Score Weight Minimum Contrast Rotation Angle Ranges Testingthe Search Algorithm on Test Images Finding Points Using Color Location Convert Pixel Coordinates to Real-World Coordinates Make Measurements Distance Measurements Analytic Geometry Measurements Instrument Reader Measurements Display Results Page Calibration Perspective and Nonlinear Distortion Calibration Defining a Calibration Template Defining a Reference Coordinate System Page Page Learning Calibration Information Specifying Scaling Factors Choosing a Region of Interest Choosing a Learning Algorithm Using the Learning Score Learning the Error Map Learning the Correction Table Setting the Scaling Method Calibration Invalidation Simple Calibration Save Calibration Information Attach Calibration Information A Technical Support Resources Web Support NI Developer Zone Customer Education System Integration Worldwide Support Glossary Numbers/Symbols A B C Page D E F G H I Page J K L M N O P Page Q R S T Page Index A B C D E F G H I Page Page L M N O P R S T V W Z