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National Instruments IMAQ Vision for Measurement Studio AcquireorReadanImage

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Chapter2 GettingMeasurement-Ready Images

©NationalInstruments Corporation 2-5 IMAQVision for LabWindows/CVI User Manual

•imaqAdd(myImageA,myImageA, myImageB);

Thisfunct ion adds twosou rcei mages and stores the result in the first

sourceimage.

•imaqAdd(myImageB,myImageA, myImageB);

This function adds two source images and stores the result in the

second source image.

Mostoperations between twoimages require that the images have the

same type and size. However,some arithmetic operations can work

between twod ifferenttypes of images (for example, 8-bi t and 16-bit).

Some functions perform operations that populate an image. Examples of

this type of operation include reading a file, acquiring an image from an

IMAQdevice, or transforming a 2D array into an image. This type of

functioncan modify the size of an image.

Some functions take an additional mask parameter.The presence of a

maskparameter indicates that the processing or analysisis dependent on

the contents of another image (the image mask). The only pixels in the

sourcei mage that are processed are those whose corresponding pixels in

the image mask arenon-zero. If an image mask pixel is 0, the

correspondingsource image pixel is not processed or analyzed. The image

mask must be an 8-bit image.

Ify ou wantto appl y ap rocessing or analysis function to the entire image,

passNULL for the image mask. Passing the same image toboth the source

imageand image mask also gives the same effect as passing NULL for the

image mask, exceptin this case the source image must be an 8-bit image.

AcquireorReadanImage

Afteryou create an image reference, you can acquire an image into your

imaging systemin three ways. You can acquire an image with a camera

throughyour image acquisition device, load an image from a file stored on

yourcomputer, or convert the data stored in a 2D array to an image.

Functionsthat acquire images, load images from file,or convert data from

a2D arrayautomatically allocate the memory space required to

accommodate the image data.

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