National Instruments IMAQ Vision for Measurement Studio - page 16

Chapter2 GettingMeasurement-Ready Images

©NationalInstruments Corporation 2-3 IMAQVision for LabWindows/CVI User Manual

Ifyo u plan to use filtering or blob analysis functions on the image, set the

appropriate border size for the image. The default border size is 3.

When you create an image,I MAQVision creates an internal image

structureto hold properties of the image, suchas its name and border size.

However,no memory is allocated to store the image pixels at this time.

IMAQVision functions automatically allocate the appropriate amount of

memory when the image size is modified. For example, functions that

acquire orresample an image alter the image size, so they allocate the

appropriate memory space for the image pixels. The return valueof

imaqCreateImage()is a pointer to the image st ructure. Supply this

pointer as an input to all subsequent IMAQVision functions.

Mostfun ctions belonging to the IMAQVision library require one or more

imagepointers. The number of image pointers a functi ontakes depends on

theimage processing function and the type of image you want to use. Some

IMAQVision functions act directly on the image and require only one

image pointer.Other functions that process the contents of images require

pointers to the source image(s) and to a destination image.

Youcan create multiple images by executing imaqCreateImage() as

manytimes as y ou want.Determ ine the number of required images through

ananalysis of your intended application. The decision is based on different

processingphases and your need to keep the original image (after each

processing step).

Atthe end of your application, dispose of each image that you created using

imaqDispose().

Table2-1. IMAQ Vision for LabWindows/CVI Image Types

Valu e Description

IMAQ_IMAGE_U8 8bit s per pixel—unsigned,standard m onochrome

IMAQ_IMAGE_I16 16bi ts per pixel—signed, monochrome

IMAQ_IMAGE_SGL 32bi ts per pixel—floating point, monochrome

IMAQ_IMAGE_COMPLEX 2×32bits p er pixel—floating point, nativeformat after a Fast

FourierTransform (FFT)

IMAQ_IMAGE_RGB 32bi ts per pixel—standardcolo r

IMAQ_IMAGE_HSL 32bi ts per pixel—color

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