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National Instruments IMAQ Vision for Measurement Studio Finding Edge Points Along Multiple Search Contours

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Chapter5 MachineVision

IMAQVision for LabWindows/CVI User Manual 5-12 ni.com

Thesefunctions require you to input the coordinates of the poi nts along the

search contour.Use imaqROIProfile() to obtain the coordinates along

the edge of each contour ina n ROI.If you have a straight line, use

imaqGetPointsOnLine()to obtain the poin tsa long the line instead of

usinga n ROI.

Thesef unctions determine the edge points based on their contrast and

slope. Youcan specify whether you want to find the edge points using

subpixelaccuracy.

Finding Edge Points Along Multiple Search Contours

UseimaqRake(),imaqSpoke(),andimaqConcentricRake()to find

edge points along multiple search contours. These functions behave like

imaqEdgeTool()behaves, but they find edges on multiple contours. Pass

in an ROIto define the search region for these functions.

The imaqRake()function works on a rectangular search region. The

search linesare drawn parallel to the orientation of the rectangle. Control

the number of search lines in the region byspecifying t he distance, in

pixels,between each line. Specify the search direction as left to right or

rightto left for a horizontally oriented rectangle. Specify thesearch

direction as top to bottom or bottom to top for a vertically oriented

rectangle.

The imaqSpoke()functio n workson an annular search region, scanning

the search lines that are drawnfrom the center of the region to the outer

boundary and that fallw ithin the search area. Control the number of lines

inthe region by specifying the angle, in degrees, between each line. Specify

the search direction as either going from the center outward or from the

outer boundary to the center.

The imaqConcentricRake()function works on an annular search

region.The concent ric rakeis an adaptation of t heR aketo an annular

region.IMAQ Visionperforms edge detection along search lines that occur

in the search regionand that are concentric to the outer circular boundary.

Control the number of concentric search lines that are used for the edge

detection byspecifying the radial distance between the concentric lines in

pixels.Specify the direction of the search as either clockwise or

counterclockwise.

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