National Instruments IMAQ Vision for LabWindows TM /CVI - page 19

Chapter 2 Getting Measurement-Ready Images

© National Instruments Corporation 2-3 IMAQ Vision for LabWindows/CVI User Manual

You can create multiple images by executing imaqCreateImage() as

many timesas you want. Determine the numb er of required images through

an analysis of your intended application. The decision is based on different

processing phases and your need to keep the original image after each

processing step. The decision to keep an image occurs before each

processing step.

When you create an image, IMAQ Vision creates an internal image

structure to hold properties of the image, such as its name and border size.

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

IMAQ Vision functions automatically allocate the appropriate amount of

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

acquire or resample an image alter the image size, so they allocate the

appropriate memory space for the image pixels. The return value of

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

pointer as an input to all subsequent IMAQ Vision functions.

Most functions in the IMAQ Vision library require one ormore image

pointers. The number of image pointers a function takes depends on the

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

IMAQ Vision 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.

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

imaqDispose().

Table 2-1. IMAQ Vision for LabWindows/CVI Image Types

Valu e Description

IMAQ_IMAGE_U8 8 bits per pixel—unsigned, standard monochrome

IMAQ_IMAGE_I16 16 bits per pixel—signed, monochrome

IMAQ_IMAGE_SGL 32 bits per pixel—floating point, monochrome

IMAQ_IMAGE_COMPLEX 2 × 32 bits per pixel—floating point, native format after a Fast

Fourier Transform (FFT)

IMAQ_IMAGE_RGB 32 bits per pixel—standard color

IMAQ_IMAGE_HSL 32 bits per pixel—color

IMAQ_IMAGE_RGB_U64 64 bits per pixel—standard color

Contents

Main IMAQ Page Important Information Warranty Copyright Trademarks Patents Contents About This Manual Chapter 1 Introduction to IMAQ Vision Chapter 2 Getting Measurement-Ready Images Chapter 3 Making Grayscale and Color Measurements Chapter 4 Performing Particle Analysis Chapter 5 Performing Machine Vision Tasks Chapter 6 Calibrating Images Page About This Manual Conventions Related Documentation IMAQ Vision NI Vision Assistant NI Vision Builder for Automated Inspection Other Documentation Introduction to IMAQ Vision About IMAQ Vision Application Development Environments IMAQ Vision Function Tree IMAQ Machine Vision Function Tree Creating IMAQ Vision Applications Chapter 1 Introduction to IMAQ Vision National Instruments Corporation 1-5 IMAQ Vision for LabWindows/CVI User Manual Chapter 1 Introduction to IMAQ Vision IMAQ Vision 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 Acquire or Read an Image 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 Complex Image Operations Making Grayscale and Color Measurements Define Regions of Interest Defining Regions Interactively Page Page Page Tools Palette Transformation Defining Regions Programmatically Defining Regions with Masks Measure Grayscale Statistics Measure Color Statistics Figure 3-4. Primary Components of a 32-Bit Color Image Figure 3-5. Primary Components of a 64-Bit Color Image Note You can also use imaqExtractColorPlanes() to process the red, green, and blue components of a 64-bit image. Comparing Colors Learning 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 Performing Particle Analysis Create a Binary Image Improve the Binary Image Removing Unwanted Particles Separating Touching Particles Improving Particle Shapes Make Particle Measurements Page Page Page Page Page Page Performing Machine Vision Tas ks Locate Objects to Inspect Page Using Edge Detection to Build a Coordinate Transform Page Using Pattern Matching to Build a Coordinate Transform Chapter 5 Performing Machine Vision Tasks National Instruments Corporation 5-7 IMAQ Vision for LabWindows/CVI User Manual Choosing a Method to Build the Coordinate Transform Figure 5-4. Building a Coordinate Transform Set Search Areas Defining Regions Interactively Defining Regions Programmatically Find Measurement Points Finding Features Using Edge Detection Finding Lines or Circles Finding Edge Points Along One Search Contour Finding Edge Points Along Multiple Search Contours Finding Points Using Pattern Matching Defining and Creating Good Template Images Symmetry Feature Detail Positional Information Background Information Training the Pattern Matching Algorithm Defining a Search Area Setting Matching Parameters and Tolerances Match Mode Minimum Contrast Rotation Angle Ranges Testing the Search Algorithm on Test Images Using a Ranking Method to Verify Results Finding Points Using Color Pattern Matching Defining and Creating Good Color Template Images Color Information Symmetry Feature Detail Positional Information Training the 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 Testing the 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 Identify Parts Under Inspection Classifying Samples Reading Characters Reading Barcodes Reading 1D Barcodes Reading Data Matrix Barcodes Reading PDF417 Barcodes Display Results Page Page Calibrating Images Perspective and Nonlinear Distortion Calibration Defining a Calibration Template Defining a Reference Coordinate System 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 and Professional Services Glossary Numbers A B Page C D E F G H I Page J K L Page M N O P Q R S T V Index Numerics A B C D E F G H I K L M N O P R S T U V W