HALCON/COM User's Manual - Image Understanding and
Contents
1. ee eee ee 6 22 1 Different Types of Classes 6 2 2 2 Classes for Special Purposes 7 2 3 Object Construction and 8 231 u y sheen u Bon OE WWO S es 8 2 3 2 CDESIUCHOT wae ea q WN eas S eri a 9 24 Interfaces and 11 2 5 11 2 6 A closer Look at Data Types 12 277 Error Handl ng gewesen ace wees tk ae 12 2 8 HALCON COM and Visual Basic 13 2 621 Object Tist ntiation a 2 342 000000000 h Mr Be hurd Mtg AT 13 2 02 Error Handl ne a 4 803 a tatu POR 14 3 Example Visual Basic Session 17 Sal First Step The GUL en pe ne nee SUN 17 3 2 Second Step 20 3 3 Final Step More Functionality 0 A 21 3 4 Other Examples runa W s PAW ae ee 22 Bibliography 25 Index 27 ii Contents HALCON COM 2000 11 16 Chapter 1 Introduction This chapter provides a short overview of the main aspects of component based software de velopment and shows how this can be done with COM The advantages and disadvantages of component based software engineering are discussed as well as the limitations as far as HAL CON is concerned2. ReduceDomain Regiongrowing Figure 3 2 Visual Basic helping you to select a method Private Sub Commandl Click Call Monkey ReadImage monkey Call Monkey Display End Sub Display Window As HWindowX Figure 3 3 Visual Basic helping you with the correct parameters 3 3 Final Step More Functionality What we have now is a very basic application which can t do very much but it needs only 10 lines of code Thus we will extend the functionality turning our application into a small image processing demo 1 Extend the variable declaration section at the beginning of your listing so it looks like this Dim Monkey As New HImageX Dim Window As HWindowX Dim Region As HRegionX Dim Eyes As HRegionX Dim State As Integer Although these declarations are not necesary Basic declares variables automatically it is nevertheless a good idea to do so 2 Check the Command1_Click subroutine and modify it like this HALCON 6 0 22 CHAPTER 3 EXAMPLE VISUAL BASIC SESSION Private Sub Command1_Click If State 3 Then End End If If State 2 Then Set Eyes Region SelectShape area and 500 50000 Set Eyes Eyes SelectShape anisometry and 1 1 7 Call Window DispObj Monkey Call Window DispObj Eyes Labeli Caption click Finish to terminate Command1 Caption Finish State 3 End If If State 1 Then Set Region Monkey Threshold 128 256 Set Region Region Connection Call
3. HALCONROOT examples vb Manual to denote a subdirectory containing an example package within the HALCON base directory referenced by the environment variable HALCONROOT 6 CHAPTER 2 THE HALCON COM INTERFACE 2 2 More about Classes Classes are the essential items to deal with when writing HALCON COM applications There are quite a lot of them and there are different types of classes thus we will have a closer look on how classes are used and what attributes they have The classes of the HALCON COM interface are partly related in a way which could be described as inheritance Therefore it is important to get an impression of how inheritance is achieved within HALCON COM and how to use it 2 2 1 Different Types of Classes There are two major categories of classes 1 classes instantiating objects that have an internal state and 2 classes instantiating objects with no internal state The first category is used to implement special data structures like images files frame grab bers etc and the operators belonging to this data whereas the second category is only used to group operators belonging together If several objects of a class belonging to the first category are instantiated they are all different from the HALCON point of view whereas the second category does not have this quality For example if we consider several objects instantiated from the image class HImageX they all denote something different they represent differ
4. It is not intended to discuss all aspects of COM in detail in this manual Thus anyone who wants to know further details about programming with COM is recommended to read the correspond ing literature 1 1 Why Components Component based software engineering has been discussed intensively in the past few years Concrete standards evolving from this discussion include DCE CORBA and COM The fas cination about components is their ability to be reused at binary level With their slight not always very complete object oriented features and the option for location transparency they form a good base for the development of modern distributed software systems In fact COM is the base for nearly every software technology Microsoft is dealing with ActiveX OLE and DirectX for example base on COM thus large parts of the Microsoft operating systems are component based Let s have a look on what a COM component looks like The main features of COM components are 1 Reuseability at binary level 2 Object orientation 3 Robust versioning 4 Location Transparency In fact the first topic is the most important in our case Binary reuseability implies that an exist ing component can be used within virtually any software development tool in any language as long as there is a certain basic support for COM in it Furthermore it does not matter what tool was used to implement the component as it is a binary standard There are numerous different too
5. and object in this manual we may speak of an uninstantiated object in that case For example if an HImageX object is created not only the referring variable is declared it is useable in terms of COM since it is instantiated but it does not yet contain any HALCON image To be a valid HALCON COM object it still must be initialized This can be done in two different ways e the object can initialize itself or e the object can be initialized by another object s method HALCON COM 2000 11 16 2 3 OBJECT CONSTRUCTION AND DESTRUCTION 9 In the first case a so called constructor is executed The term constructor is somewhat misleading here since it has a slightly different meaning than for example a C constructor In C terms a constructor is a special method always named exactly as the class which does the object construction automatically without the need to be called explicitly In the HALCON COM case a constructor is an ordinary method which initializes the object s internal state and must be called explicitly For that reason a HALCON COM class can have many differently named constructors of the constructors of our example HImageX class is ReadImage which initializes the object by reading an image file from the hard disk Another way to initialize an object is to get it as result after calling another object s method For example an uninitialized HImageX object becomes initialized when it is returned fr
6. 27 HALCON window 7 HalconX 5 HDevelop 7 HImageX 20 HImageX 7 8 HWindowX 20 HObjectx 7 HOperatorSetX 7 8 HRegionX 7 HSystemX 12 HTuple 12 HUntypedObjectX 7 8 HWindowX 7 HWindowXCtr 7 IDispatch 2 IHImageX 11 IHObjectX 11 implementation 2 inheritance 2 5 11 inheritance simulation 5 initialization 8 instantiation 8 interface 2 interfaces 5 11 internal state 6 IUnknown 2 Java 2 Label 18 language independence 1 late binding 3 library 5 location transparency long 12 meaning of objects 6 member 2 memory management 9 method 2 methods 5 11 28 naming convention 5 New 14 20 Nothing 14 object 2 object browser 17 object copying 9 object destruction 9 object duplication 9 object initialization 20 object instantiation 20 object orientation 1 OLE 1 On Error 14 pointer 8 11 polymorphism 2 properties 5 11 property 2 put properties 11 reference 11 Resume Next 15 semantics of objects 6 Set 14 special classes 7 strong typed 7 top level window 7 type conversion 8 variable 9 variable declaration 20 21 VARIANT 12 versioning Visual Basic 2 13 VisualC 1 weak typed 7 HALCON COM 2000 11 16 Index Index 29 HALCON 6 0
7. An example illustrating the possibilities for interactive image processing applications HALCONROOT examples vb Tools Calibration An example showing how to calibrate a camera HALCONROOT examples vb Tools Matching An example showing how to use shape based matching HALCONROOT examples vb Tools Measure A real world measurement example showing how to measure the pins of an IC HALCONROOT examples vb Manual The example described in this chapter HALCON 6 0 24 HALCON COM 2000 11 16 CHAPTER 3 EXAMPLE VISUAL BASIC SESSION Bibliography Arm98 Tom Armstrong Active Template Library A Developer s Guide M amp T Books Foster City CA 1998 Bro95 Kraig Brockschmidt Inside OLE Microsoft Press Redmond Washington 1995 25 26 HALCON COM 2000 11 16 BIBLIOGRAPHY Index abstract class 5 6 ActiveX 1 ActiveX container 7 ActiveX control 7 aggregation 2 7 base class 5 7 8 binary reuseability 1 binding 3 BSTR 12 Call 13 Cast 7 9 class definition 2 classes 5 6 code generation 8 CommandButton 18 component constructor 9 11 containment 2 data members 11 data type 6 7 default interface 11 Delphi 1 derived class 7 11 Dim 13 DirectX 1 double 12 early binding 3 encapsulation 2 error handling 12 error offset 12 ErrorBaseCOM 12 ErrorBaseHalcon 12 example 17 form 17 get properties 11 group class 6 GUI 17
8. Of course you must have knowledge about the language tool you plan to develop with e g Visual Basic This manual is divided into the following parts e Introduction This chapter provides a short overview of COM concepts in general e The HALCON COM Interface This chapter describes the structure of the HALCON COM interface giving a quick overview though not getting very deep into the details e Example Session In this chapter a small image processing demo application is developed stepwise with Visual Basic Release Notes Please note the latest updates of this manual e 274 Edition HALCON 6 0 October 2000 Revision of the structure of the manual and minor updates Contents 1 Introduction 1 1 1 Why Components 1 1 1 1 Interfaces and COM 2 1 1 2 Objects Methods and Data Members 2 1 1 3 Inheritance and Polymorphism 2 2 1 1 4 1 3 1 2 HALCON and COM 2 5442 Sele Gord peq P w oud book So 3 E21 AdNVa688668S1 2 Z So at Mm ke s Hi A Pa SUS a 3 12 2 Disadvantages sab ua b ucu Oe rer 3 122 3 ATU CANTONS akg a h Sa deer ig k 4 1 3 Additional Sources of Information 4 2 The HALCON COM Interface 5 21 PIECE oe s s E EEE ET ER S Y ES 5 2 2 More about Classes 4
9. The reason for the New keyword in the first line is that we want the HImageX object to be instantiated e g memory being allocated for it This is not necessary for the HWindowX since it is already instantiated itis the ActiveX control we have drawn inside the form The object Monkey is instantiated as we know although it is not yet initialized with an image but the Window variable still refers to nowhere Insert another line into the Form_Load subroutine Private Sub Form_Load Set Window HWindowXCtrli Object Labeli Caption Click Next to start End Sub Now the Window variable refers to the HWindowX part of our ActiveX control Switch to Commandi Another subroutine shows up which you have to complete like this Private Sub Commandi_Click Call Monkey ReadImage monkey Call Window DispObj Monkey End Sub While typing you will notice a very convenient Visual Basic feature since it knows the methods of a class it allows you to select one from a list if you wish to do so see figure 3 2 You will also get assistance in supplying the parameter values for a method call in the right order and with the right types See figure 3 3 HALCON COM 2000 11 16 3 3 FINAL STEP MORE FUNCTIONALITY 21 6 Start your application by pressing F5 and see what happens Private Sub Commandl Click Call Monkey Rel Call Monke e End Sub Readlmage ReadSequence RealToComplex Rectangle 1Domain
10. As Long Dim SysObject As New HSystemX On Error Goto myErrorHandler lt some code gt myErrorHandler do something with the error information for example Debug Print Error occurred Err Description LastErrorCode Err Number SysObject ErrorBaseHalcon Resume Next If an error occurs in lt some code gt an immediate jump to the label myErrorHandler is made where an arbitrary error processing mechanism can be placed The scheme used in the exam ple tries to model a traditional procedural error recovery strategy where every function call returns an error code which has to be checked before program execution can continue When an error occurs the error handling code at the corresponding label takes over writes a status HALCON COM 2000 11 16 2 8 HALCON COM AND VISUAL BASIC 15 message the textual error representation to the Visual Basic Immediate window and stores the error code in a global integer variable The global Visual Basic object Err is the source of information in this case Afterwards control is put back to the line following the statement which produced the error This is done by the Visual Basic command Resume Next The next line of code then would be responsible for checking the error code stored in LastErrorCode Of course this method is a little long winded and not quite up to date an exception handling mechanism in general is much more flexible and robust but it s quite easy to unders
11. E Alphabetic categorized 2 Project Project1 5 5 Forms A Labell ca 0 Left Justify Formi Form1 a 1 30 ve False ca amp H8000000F8 1 Opaque an 3 0 None oo Label Caption EJ Returns sets the text displayed in an object s title bar or below an object s icon D HalconX example Formlayout lt Figure 3 1 Having performed all the steps from 3 1 you should end up with a setup like this HALCON 6 0 20 3 2 CHAPTER 3 EXAMPLE VISUAL BASIC SESSION Second Step Functionality Now you have the GUI finished you should go ahead and make the application do some thing 1 Right click somewhere inside the form and select View Code Another window will pop up over the form with two combo boxes at its top border Select Form from the left combo box You will see the code to be executed when the form is created Insert a line into the subroutine Private Sub Form_Load Labeli Caption Click Next to start End Sub You just changed the text the label at the bottom will show when the application is launched Next we will declare some important variables switch back to General in the left combo box above the source code window and insert in the following lines at the top Dim Monkey As New HImageX Dim Window As HWindowX Some online selection boxes for the desired object type will assist you We have just created two objects a HImageX and a HWindowX
12. HOperatorSetX is that all its methods exclusively use HObjectX type input iconic parameters and return HUntypedObjectX type output iconic objects Note it is allowed to have input parameters HALCON 6 0 8 CHAPTER 2 THE HALCON COM INTERFACE of an abstract type C programmers will know this concept it corresponds to passing objects through a pointer to their abstract base class However this is not allowed for output parameters Here the data type must be specified because there has to be some typed vari able which can store the output object Since HOperatorSetX methods must use a generic data type scheme output iconic objects are always of type HUntypedObjectX Hand written COM code should not make use of HOperatorSetX HUntypedObjectX concept since it weakens the otherwise strong typed object oriented approach it becomes relevant only in cases where automatically generated code is involved 2 2 2 4 The Method Cast All classes derived from HObjectX supply the Cast method which is used for type conver sions between the concerned classes This method breaks up the well defined data type scheme evolving from the class hierarchy so it should not be used except when there is no other possi bility By using the Cast method an image object can be turned into a region an XLD can become a HUntypedObjectX object and so on The reason for that is as mentioned above the need to convert back and forth to the HUntypedObject
13. Window SetColored 12 Call Window DispObj Region Labeli Caption Next the ape s eyes will be selected State 2 End If If State 0 Then Call Monkey ReadImage monkey Call Window DispObj Monkey Labeli Caption Next the image will be segmented into several regions State 1 End If End Sub 3 Run your little program and enjoy a guided tour through a very common image process ing example 3 4 Other Examples There are some more pre coded examples so you can discover how things work with HALCON COM These examples can be found under the following directory HALCONROOT examples vb The following list shows all the supplied examples and explains their topics in short To experi ment with these examples we recommend to create a private copy in your working directory 1 HALCONROOT examples vb Applications FA An example showing how to use correlation based pattern matching HALCON COM 2000 11 16 3 4 OTHER EXAMPLES 23 10 HALCONROOT examples vb Applications Monitoring An example showing how to use a background estimator for traffic monitoring HALCONROOT examples vb Online Barcode An online example showing how to read barcode HALCONROOT examples vb Online Measure An interactive example showing how to use the measure tool HALCONROOT examples vb Online Movement An example showing how to discover movement by using the difference of images HALCONROOT examples vb Segmentation
14. be the base class for other classes if it should be of any use The idea behind this concept is that abstract classes provide a semantic base for their derived classes without being concrete enough for HALCON COM 2000 11 16 2 2 MORE ABOUT CLASSES 7 instantiation A look on real world terms reveals many analogous cases there is for example the class animal which can be seen as an abstract base class for classes like fish bird and horse Any existing being can not be only an animal it is always either a fish a bird or a horse or whatever else There is only one such abstract class in the HALCON COM interface HObjectx It represents a HALCON iconic object such as an image a region or an XLD The derived classes HImageX HRegionX and so on then specify the exact type of the HALCON iconic object see also the class overview in figure 2 1 2 2 2 Classes for Special Purposes There are some HALCON COM classes that have special jobs Although they do fit into the above systematics they are worth mentioning because they have to be used in a specific way or show some specific semantics 2 2 2 1 HWindowXCtrl This class is a HALCON window in the form of an ActiveX control Its advantage against the ordinary HALCON window HWindowX is the possibility to exist inside an ActiveX con tainer An ActiveX container is a part of a window which can contain GUI elements such as buttons sliders and so on When developing complex image processi
15. interface and the related class are the same most of the time Actually an interface behaves similar to a C pointer or reference to an object and that is exactly what Visual Basic tries to hide As said before interfaces are used for inheritance simulation within HALCON COM the way this works is simple We have seen that HObjectX is an abstract and thus not instantiable class On the other hand the derived classes HImageX HRegionX etc have to supply their own functionality plus the inherited HObjectX functionality This is done with the help of interfaces currently there is no COM class named HObjectX thus no HObjectX object can be initialized only an interface named IHObjectX This interface appears in all derived classes together with their default interfaces HImageX for example has two interfaces in fact it has a hidden third one 1 IHImageX the default interface and 2 IHObjectX the inherited interface This allows to satisfy every method which expects a HObjectX parameter actually it expects a reference to that class in form of the IHObjectX interface with any derived class object as such an object always has the IHObjectX interface too This corresponds to a certain object oriented rule which allows an automatic cast from the derived class to the base class not the other way How intuitive this feature can be used again depends on the client language tool Visual Basic 5 0 for example only regards the defaul
16. received code The offset is a read only property of the HSystemX class There are two offsets one for the HALCON COM interface and one for HALCON itself Those properties are named e HSystemX ErrorBaseCOM and e HSystemX ErrorBaseHalcon HALCON COM 2000 11 16 2 8 HALCON COM AND VISUAL BASIC 13 In order to get the correct HALCON error code a HSystemX object must be instantiated one is enough for the whole application anyway since HSystemX objects have no identity Then the value of the respective HSystemX property must be subtracted from the returned error code to get the correct HALCON error code For an example how to deal with error codes see section 2 6 2 2 8 HALCON COM and Visual Basic So far the important basics of the HALCON COM interface have been explained Now let s have a look at what things behave like when using Visual Basic 2 8 1 Object Instantiation There are many different ways to instantiate COM objects in Visual Basic We will discuss only one of them because it has certain advantages over all the others We have seen in the sections before that a distinction should be made between the instantiation and the initialization of ob jects Even more important we should also distinguish objects from object reference variables An object reference variable is set up by its declaration with the keyword Dim Dim imagei As HImageX This statement does not yet create a COM object it just declares a v
17. HALCON Version 6 0 MI MVTec Software GmbH HALCON COM User s Manual How to use the image analysis tool HALCON Version 6 0 in your own COM programs All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photocopying recording or otherwise without prior written permission of the publisher 1 Edition April 1999 2 Edition October 2000 EC Copyright 1999 2000 by MVTec Software GmbH M nchen Germany Microsoft Windows Windows 95 Windows NT Windows 2000 Visual C and Visual Basic are either trademarks or registered trademarks of Microsoft Corporation All other nationally and internationally recognized trademarks and tradenames are hereby rec ognized More information about HALCON can be found at http www mvtec com halcon About This Manual This manual gives an overview of the HALCON COM interface COM component object model is a Microsoft standard for component based language independent software develop ment This manual contains all necessary information to install the COM interface and under stand its main concepts a guided example shows how to develop HALCON applications using Visual Basic This manual is intended for the advanced HALCON user You should be familiar with the main HALCON package and have experience in developing image analysis applications with HDevelop
18. X objects used by the HOperatorSetX methods For example if an automatically generated code fraction produces an object variable of type HUntypedObjectX which shall be used in some hand written code as an image it can be forced to become a HImageX object Of course it must be assured that the variable really does contain an image it is the programmer s task to take care for that We will have a closer look on how to use the Cast method later on 2 3 Object Construction and Destruction 2 3 1 Construction A HALCON COM object can be in different states It can be instantiated and it can be ini tialized An instantiated object need not necessarily be initialized but an initialized object is always instantiated Instantiation means using an appropriate technique to produce a living COM object this techniqe differs according to what client language is used Initializing means giving the object a well defined internal state There is another state an object can have it is neither instantiated nor initialized Since not being instantiated means not existing what exactly does this condition mean The answer depends somewhat on the client language used but is rather easy to understand if we realize that COM object variables actually are references to an existing or not existing object Thus if such a variable is declared there is not necessarily yet an object created it refers to As we like to mix up the terms reference to an object
19. an place inside your form They are represented as small icons Move the mouse cursor over the different icons to see the bubble help revealing their names You should find an icon showing the HALCON symbol named HWindowXCtr1 You guessed it That is our ActiveX control HALCON window 7 Activate the HWindowXCtrl icon Draw a rectangular region inside the form make sure it is approximately square When releasing the mouse button the square area should turn black 8 Switch to the CommandButton icon looking like a brick in the left tool bar Draw a button inside the form beside or below the HALCON window Change the button s caption text to Next gt gt in the properties box 9 Now switch to Label in the tool bar and draw a longish rectangular area at the bottom of the form If you encounter placement difficulties due to lack of form space you can always resize the form to fit your needs 10 Resize the form so that it fits around the before created items Now you have the entire GUI for your application ready to go and your screen should look similar to figure 3 1 HALCON COM 2000 11 16 3 1 FIRST STEP THE GUI 19 Project Microsoft Visual Basic design Form Form Is gt 3 Eile Edit View Project Format Debug Run Tools Add Ins Window Help le S H b m W Li 120 5280 1 4332 492 x 2800759 x General Label1 Label oslo
20. ariable able to reference a HImageX object If we want to declare a reference variable and immediately create an object it refers to we should write Dim imagel As New HImageX Now a new HImageX object is created and the variable image refers it Note variable declaration is not a must with Visual Basic but should always be done anyway Undeclared variables get declared automatically when referenced and that can lead to errors which are very hard to discover It is a good idea to place the statement Option Explicit on top of every Visual Basic module because then variable declaration is forced We now have a valid COM object to which the declared variable refers To initialize this object we could call a constructor method Dim imagei As New HImageX Call image1 ReadImage some_file_name Note the Call keyword It s necessary in Visual Basic if the called method doesn t return a value The other way of initialization would be using another object s method Dim imagel As New HImageX Dim regioni As HRegionX Call image1 ReadImage some_file_name Set regionl imagei Threshold 128 255 HALCON 6 0 14 CHAPTER 2 THE HALCON COM INTERFACE There are two important things here First the Set keyword it replaces the Call keyword when the called method returns another COM object in this case a region Furthermore the second variable declaration omits the New keyword This is because the corresponding varia
21. ble need not instantiate an object at declaration time This is done within the Threshold method which creates a new COM object itself and passes a reference to this object as its return value HALCON COM objects get destroyed as soon as no variable references them anymore For local variables this is the case when they go out of scope e g a subroutine is left For global variables or if an explicit destruction is desired this has to be done by the user Dim imagei As New HImageX Dim regioni As HRegionX Call image1 ReadImage some_file_name Set regionl imagei Threshold 128 255 Set imagel Nothing Set regioni Nothing Here both variables are assigned the special Visual Basic keyword Nothing which denotes that they do not reference their related COM objects anymore These COM objects thus are not referenced at all which leads to their immediate destruction There is of course a lot more to say about Visual Basic HALCON programming Some further aspects might become clear in the following example session 2 8 2 Error Handling When using Visual Basic errors can be trapped by an error handler If no custom error handler is present Visual Basic itself supplies a default one which shows a message box containing the textual error description Error handlers in Visual Basic can be set with the keyword On Error To trap an error in a portion of code the apropriate construct could look like this Dim LastErrorCode
22. e because they are not directly relevant for working with the HALCON COM interface Thus you are recommended to read additional COM related literature and or the documentation of your preferred develop ment tool e g Visual Basic At least you should be familiar with object oriented concepts like inheritance classes and methods in order to understand the following chapter 2 1 Preface Let s have a closer look at the HALCON COM interface The whole package called the HalconX library contains all the functionality partitioned into several classes Each class has one or more interfaces that are built up from methods and properties The HALCON COM interface uses inheritance and thus contains derived classes and also an abstract base class Since COM is not meant to supply a standardized inheritance mechanism HALCON COM makes extensive use of interfaces to simulate inheritance we will discuss this topic more detailled afterwards Naming Conventions classes are capitalized and begin with an H They always end with an upper case X for example HFramegrabberX interfaces are also capitalized and end with X but begin with an T for example IHObjectX methods properties and parameters are capitalized for example GrabImage FileName Since COM is only available for the Windows operating systems family all file paths and envi ronment variables in this manual are printed in the Windows NT convention e g
23. ent HALCON images However if we have an object of a class like HSystemX that represents the internal state of the HALCON kernel it does not matter how many of those objects will be instantiated because all of them denote the same there is only one HALCON kernel to be rep resented Those classes can be understood as group classes denoting that they supply a bunch of methods that all have some semantic peculiarities in common In contrast to this methods of the first category classes may share a common semantics but work on different data For example if an object of the HImageX class is instantiated its methods always work exactly on one specific HALCON image the one that is represented by the object to be precise a HImageX object may also represent an array of images Different HImageX objects represent different images and therefore work on different data From an object oriented point of view classes and data types are the same so that all of the HALCON COM classes can be seen as data types To make a long story short it does not make much sense to see the second category classes as data types because they have no meaning That s why they will never show up as a method parameter Beseides the first two groups we can categorize classes in another way well known in the object oriented world 1 abstract classes and 2 non abstract classes A class is called abstract if it can not be instantiated Thus an abstract class must
24. ice Pack 4 or Windows 2000 and Visual Basic 6 0 3 1 First Step The GUI Go ahead and 1 Launch Visual Basic A dialog named New Project should appear allowing you to select the type of project you want Switch to New in the tab list select Standard EXE and click Open 2 Select Project from the menu bar and click Components A dialogue box shows up listing the components installed on your system Switch to Controls in the tab list and place a check next to the item HalconX typelibrary V1 0 3 Press F2 The object browser should appear See if you can find HImageX and browse through some of the corresponding methods Clicking on a method shows its parame terization as well as a short help text about what it will do in the status area at the bottom of the object browser Close the object browser 4 Have a look at the dialogue template form showing in the lower half of the screen it should be titled Form1 In the upper half you will discover an area titled Properties Formi Here you can set and retrieve the active GUI object s in this 17 18 CHAPTER 3 EXAMPLE VISUAL BASIC SESSION case the form s properties Click on Form1 right beside Caption and change the string to HalconX example You should see the effect of your action immediately in the cap tion text of the below form 5 Grab the form and resize it to a suitable extent 6 Have a look at the tool bar to the left here you can find all the control elements you c
25. lder interfaces Another reason for multiple interfaces is the ability to partition a component s functionality into several well defined portions There are also a couple of standard COM interfaces every component has by default those are mainly IUnknown and IDispatch They are not described in this manual so that interested readers are refered to the appropriate literature 1 1 2 Objects Methods and Data Members Keeping the C point of view we come now to the question what are the objects methods and data members of a class in terms of COM Just as with C classes there are interfaces in COM and those interfaces are made up from some methods Several objects of a class correspond to several instances of a component each with its own internal state However there are some differences with data members as their handling within COM depends on the tool the component is used by COM follows a concept of properties that are special methods allowing tools like Visual Basic to treat them just like data members With C they still are only methods thus there is no way to modify and retrieve data members directly From this point of view COM class data members can be compared with C private class members 1 1 3 Inheritance and Polymorphism As COM is a binary standard inheritance must also take place at binary level which makes the process slightly uncomfortable Without going into detail one can say that the only thing of interest here is tha
26. ls for developing COM components e g MS Visual C Borland C and Delphi MS 2 CHAPTER 1 INTRODUCTION Visual Basic MS J and a lot more The object oriented characteristics of COM components such as encapsulation inheritance and polymorphism ease the development of software espe cially for those programmers that are already familiar with object oriented programming e g with C The versioning and location transparency features of COM components will not be discussed any further here as they are less important for developing software with HALCON and as they are not yet completely tested and implemented with the current revesion 1 1 1 Interfaces and COM An important aspect of COM is the usage of component interfaces Compared to the C ter minology an interface corresponds to the declaration of a class thus showing its functionality and hiding the internal implementation details This encapsulating feature makes it possible to efficiently use a COM component without the need to know anything about its implementation However unlike a C class a COM component can have multiple interfaces Seeming rather strange at first glance the motivation for this gets clearer when looking at the versioning aspect once defined an interface stays exactly the way it is newer versions of the component then de fine enhanced or extended functionality by new interfaces allowing existing software to remain unchanged because it can still use the o
27. mation what kind of data it contains Also a combination of different or equal values is possible just like with HTuples The main difference is that a VARIANT is no class This implies the complete absence of any methods So all the additional functionality of the very powerful HTuple class must be accessed in another way For that reason there is a HTupleX class which groups methods for tuple operations like vector addition string concatenation and so on Another important and widely used COM data type is BSTR This standard COM flavor of character strings is not directly compatible with standard C like string implementations mainly because it uses wide chars This means that auxiliary functions must be used to access or modify BSTRs when using C C Again this means no problem with Visual Basic as it is the default string data type there Additionally there are integral data types like long and double as well They are used in situations where array or multitype parameters are not allowed or make no sense 2 Error Handling The HALCON COM interface uses the standard COM error handling technique where every method call passes both a numerical and a textual representation of the error to the calling framework It is then up to the caller to react to this information Since low error numbers are reserved for COM HALCON COM uses a very high offset to its own error codes To get the correct HALCON error code this offset must be subtracted from the
28. ng applications it is often necessary to integrate all user interaction components input and output seamlessly into one surface The HWindowX type HALCON window does not provide this flexibility since it always appears as a top level window In order to behave like an ordinary HWindowX HAL CON window HWindowXCtrl uses the COM technique of aggregation Thus any new created HWindowXCtrl type ActiveX control automatically instantiates a HWindowX object which is bound to the control 2 2 2 2 HUntypedObjectX HUntypedObjectX is derived from HObjectX just like HImageX HRegionX and so on Its purpose is to get an instantiable form of the abstract base class The class does not have any members as it just consists of a polymorphic data type without any special meaning As it is this weak typed it can not be used together with the strong typed methods of the other classes except by using the Cast method which allows arbitrary type conversions between all HObjectX derived classes explained later on HUntypedObjectX is meant to be a generic data type used by the special class HOperatorSetX 2 2 2 3 HOperatorSetX This is basically a group class for all existing HALCON operators HOperatorSetX is meant to provide access to a procedural way of HALCON programming The reason for that is the fact that it is easier for some non object oriented tools like HDevelop to generate COM code automatically when using a procedural technique The specificity about
29. nge the internal state of an object whereas the get property only allows to read out the internal state Usually but not always both types are present acting like an ordinary variable class member in C The properties in the HALCON COM interface are just for convenience purposes since they always map to an existing method The HWindowX class for example has quite a lot of properties Width and Height define the window s extent Draw sets or gets the current drawing mode and so on All of these properties are mapped to their corresponding methods Reading out the draw mode for example results in a call to the Method GetDraw whereas Width Height both are mapped to the method GetWindowExtent when retrieving values and SetWindowExtent for changing values respectively 2 6 Acloser Look at Data Types We have seen that a lot of the data types used within the HALCON COM interface are actually the classes themselves But there are also more basic everyday types being used A widely used data type in the COM world and thus in Visual Basic is the VARIANT type All users of the HALCON C interface will know the HTuple data type which is both polymorphic it can be one of several different subtypes and supplies array functionality it can hold several data items at once VARIANTs behave analogously and are the COM equivalent for HTuples Exactly like a HTuple a VARIANT is able to hold data of different basic types plus the infor
30. nment the first must be performed by some automatic destruction process To pick up the HImageX example again the automatic destructor must free the image data using the HALCON memory management Another example if a top level HALCON window gets initialized it is physi cally opened The automatic destructor must take care of the window getting closed before the according COM object finally gets destroyed HALCON 6 0 CHAPTER 2 THE HALCON COM INTERFACE 10 pzp _ lt gt aa Reco e a E gt Fe HWindowxCtril Abstract Class PSS Aggregation Class instantiating objects which have an internal state NY lt gt Class instantiating objects which have no internal state Figure 2 1 An overview of the HALCON COM class hierarchy HALCON COM 2000 11 16 2 4 INTERFACES AND INHERITANCE 11 2 4 Interfaces and Inheritance As said before COM classes are built up from interfaces which in turn contain methods and properties Each HALCON COM class has got one default interface named accordingly to the class For example the class HImageX contains the default interface IHimageX which provides all the relevant methods Dealing with interfaces is strongly related to the client environment used so we will not have a too close look at this topic now For example Visual Basic tries to completly hide the whole interface topic from the user in that case an
31. om a call to MeanImage which does a convolution on an image and produces another image Note the mechanism is indeed slightly more complicated and again depends on the client language In fact an object variable needs not refer to a living COM object when being used as a return value of a method call Even more if it does the referred object gets destroyed before the new object is assigned to the variable Actually there is yet another way to initialize a HALCON COM object by using the Cast method mentioned before The cast method takes another object of a related derived from HObjectX class as parameter which in turn has to be initialized Then the object the calling method belongs to gets initialized with the internal state of the other object Because no copying or duplication takes place the other object gets uninitialized Note Not all HALCON COM objects can have this initialized state An object can only be initialized if it has an internal state Thus all the group classes from 2 2 1 must be excluded Therefore they have no constructor methods 2 3 2 Destruction We have seen that creating a valid HALCON COM object is a two step process first the COM object needs to be instantiated then it must be initialized This implies also a two step de struction process to destruct an object it must be uninitialized before being destroyed which is the opposite of being instantiated The latter is done by COM and the client enviro
32. ormation you may consult the following manuals e Getting Started with HALCON An introduction to HALCON in general including how to install and configure HAL CON e HDevelop User s Manual An introduction to the graphical development environment of the HALCON system e HALCON C User s Manual How to use the HALCON library in your C programs e HALCON C User s Manual How to use the HALCON library in your C programs e Extension Package Programmer s Manual How to extend the HALCON system with your own operators e Frame Grabber Integration Programmer s Manual A guide on how to integrate a new frame grabber in the HALCON system Note that in some cases you might define new operators using the Extension Package Interface instead of using the standard HALCON Frame Grabber Integration Interface in order to exploit specific hardware features of a frame grabber board e HALCON HDevelop HALCON C HALCON C HALCON COM The reference manuals for all HALCON operators versions for HDevelop C C and COM All these manuals are available as PDF documents The reference manuals are available as HTML documents as well For the latest version of the manuals please check http www mvtec com halcon HALCON COM 2000 11 16 Chapter 2 The HALCON COM Interface This chapter describes the structure of the HALCON COM interface Please note that there are several interesting facts to know about COM that are not discussed her
33. re the specification must be available in a format that fits the used programming language e g when using C as client language one would typically include the header files containing the method declarations Otherwise the programmer could make the methods being bound at runtime then no language dependent information is needed for compiling and the calling mechanism is totally different Again we will not go into details and thus only point out the main aspect that runtime bound methods calls are somewhat slower than their early bound counterparts The HALCON COM interface supports both early and late binding so that special needs of different applications can be satisfied 1 2 HALCON and COM 1 2 1 Advantages How can the user of HALCON profit from a COM interface The main advantage is that with a COM interface the powerfull image processing features of HALCON can be used by a wide range of applications and development tools so that its usage is no longer restricted to C and C The world of Visual Basic Delphi and other tools stands open for the development of HALCON applications Beside this another important advantage of a COM interface lies in the widespread standard HALCON is joining with it nearly any piece of software related to Windows is also related to COM This will not change in the near future and upcoming new de velopment tools will be firmly bound to COM anyway Further versions of the HALCON COM interface might also suppor
34. t COM s ability to enable multi client multi threaded application development with method calls across process and machine boundaries 1 2 2 Disadvantages Of course COM can also show some disadvantages and using HALCON in a component based way can be rather tricky depending on the language and tool one is using for development For example it is really easy to use software components with Visual Basic but this is not neces sarily the case when considering VisualC here the classic HALCON C interface is far more convenient As said before COM shows some other powerful features like options for distributed computing that may be supported in future HALCON releases Then the HAL CON COM interface should be a big step ahead the other language interfaces HALCON 6 0 4 CHAPTER 1 INTRODUCTION 1 2 3 Limitations Although the complete functionality of the HALCON library can be used without limitations there exist some limitations for the current version of the HALCON COM interface e Parallel HALCON has no language interface to COM because Microsoft Visual Basic the main development tool for COM programs does not support real multi threading If you need the features of Parallel HALCON automatic parallelization or reentrancy please use the C or the C interface e Currently the HALCON Extension Package Interface cannot be used to create extension packages for COM 1 3 Additional Sources of Information For further inf
35. t interface an object supplies and treats that as if it was the class itself That implies that only the methods contained in the default interface seem to belong to a class Thus to also use the inherited methods contained in the IHObjectX interface an explicit cast to the base class is necessary This is a widely known Visual Basic weakness and may get improved by Microsoft in forthcoming versions 2 5 Methods and Properties There is not much to say about methods since they can be used quite intuitively The only interesting aspect here is the fact that different classes can have methods with the same name but with a different parameter configuration These methods perform the same action as their identical names let expect but show a different point of view For example the method GrabImage that retrieves an image from a frame grabber is part of the HImageX as well as of HFramegrabberX class In the first case the method is a constructor for an image object and takes a HFramegrabberX object as parameter that denotes the frame grabber from which to retrieve the data In the second case the method takes the HImageX object into which the image should be grabbed as parameter Properties are a special COM feature and can be treated like data members by tools like Visual Basic There are two kinds of them put and get properties A put property allows the user HALCON 6 0 12 CHAPTER 2 THE HALCON COM INTERFACE to cha
36. t there are two methods of reusing existent components containment and aggregation Both techniques are commonly used by C programmers as well contain ment corresponds to C classes instantiated as a member object in other classes whereas aggregation roughly corresponds to inheritance The main difference between containment and aggregation is the way the interface s of the contained aggregated component s are handled the methods and properties of a contained component are hidden to the outside so that only the containing component can use them Any method that should be visible from outside has to be HALCON COM 2000 11 16 1 2 HALCON AND COM 3 re defined in the outer component In contrast to this the interface s of an aggregated com ponent are merged with the interfaces of the aggregating one thus automatically making their methods visible to the outside The object oriented feature of polymorphism is also achieved through interfaces different COM classes exposing the same interface can be understood as showing polymorphic behaviour as they act differently responding to the same methods 1 1 4 Early and Late Binding Binding is the process of resolving the call adresses of a component s exposed methods This can be done at compilation time early binding or at runtime late binding Thus when using a component a programmer can take a specification of the contained methods and integrate it directly into the application Therefo
37. tand We have seen that there are two types of errors HALCON related errors and COM interface related ones Since the COM interface errors have smaller error numbers than the HALCON error codes the above mechanism would lead to negative numbers In that case the produced error code would have to be subtracted from SysObject ErrorBaseCOM to get the correct then interface related error code HALCON 6 0 16 CHAPTER 2 THE HALCON COM INTERFACE HALCON COM 2000 11 16 Chapter 3 Example Visual Basic Session In this chapter you will learn how to develop HALCON applications quickly using Microsoft Vi sual Basic and the HALCON COM interface There will be simple steps describing what to do The result will be a very small exemplary vision application with doubtful value but equipped with a graphical user interface As an additional source of information you are strongly encour aged to have a look at the other examples which are supplied as Visual Basic sources together with HALCON The program developed in this chapter is also available ready to go in the HALCONROOT examples vb Manual directory together with other examples How ever it is recommended to follow the steps below and program it yourself as you will get a better impression of how Visual Basic program development works and gain a lot of additional information with the single steps Please note that to use HALCON COM inside Visual Basic you need Windows NT 4 0 with Serv
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