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Advanced Recognition Sample

  • Article

The advanced recognition sample demonstrates advanced features of the Microsoft Tablet PC Automation application programming interface (API) used for handwriting recognition.

It includes the following features:

  • Enumerating the installed recognizer
  • Creating a recognizer context with a specific language
  • Using the recognizer object
  • Setting recognition factoid and word lists
  • Using guides to improve the recognition quality
  • Dynamic background recognition
  • Gesture recognition

The interfaces used are: IInkRecognizer, IInkRecoContext, IInkRecognitionResult, IInkRecognitionGuide, IInkWordList, IInkGesture, IInkCollector, IInkDisp, IInkRenderer, IInkDrawingAttributes, IInkStrokes, and IInkStroke.

Ink and Project Headers

First, include the headers for Tablet PC Automation interfaces. These are installed with the Tablet PC Platform SDK. The TpcError.h file contains the Tablet PC API Error Code definitions.

#include <msinkaut.h>
#include <msinkaut_i.c>
#include <TpcError.h>

The EventSinks.h file defines the IInkEventsImpl and IInkRecognitionEventsImpl interfaces, and sets up the RecognitionWithAlternates, Stroke, and Gesture events.

#include "EventSinks.h"

The ChildWnds.h file contains the definitions of the classes CInkInputWnd and CRecoOutputWnd, which are derived from the ATL's CWindowImpl and used for creating the sample's child windows.

#include "ChildWnds.h"

The AdvReco.h file declares the CAdvRecoApp class, which is the application window class for this sample.

#include "AdvReco.h"

Initializing the Application Window

The window's Run method sets up the CAdvRecoApp object, loads the menu and icon for the window, creates an InkRecognizerContext object for the default recognizer, and starts the window's message loop.

The window's OnCreate method handles the WM_CREATE event and creates the child windows. An InkCollector object connects to the ink collector's event source, and enables ink input on the input window. Then it creates an InkRecognizerGuide object and uses the ink collector's Renderer property to convert the recognition guide box rectangles to ink space. Finally, the OnCreate method creates an InkWordList object.

Handling Ink Collector Events

The window's OnStroke method handles the ink collector's Stroke event. The new IInkStrokeDisp object is added to the InkStrokes of the ink collector's Ink property.

The window's OnGesture method handles the ink collector's Gesture event. The OnGesture method identifies the gesture, using the highest confidence gesture first, and checks if the window supports this particular gesture. If the gesture is supported, the gesture's bounding box is invalidated, as the gesture is removed from the strokes collection. If the gesture is not supported, the Gesture event is canceled, which causes the ink collector to raise a Stroke event. Finally, the results window is updated.

Handling Recognizer Context Events

The window's OnRecognitionWithAlternates method handles the recognizer context's RecognitionWithAlternates event. The OnRecognitionWithAlternates method displays the recognition results in the results window.

Handling Menu Commands

The window's OnRecognizer method handles the commands on the Recognizer menu. If the Default command was selected, the GetDefaultRecognizer method of the InkRecognizers is used to retrieve the default recognizer; otherwise, the selected recognizer is retrieved. Then, a recognizer context is created and used, and menu and status bar are updated.

The window's OnFactoidWordlist method handles the Use Wordlist command on the Factoid menu. The recognizer context's Strokes property is set to NULL to reset the recognizer context. If the Use Wordlist option is turned off, the recognizer context's WordList property is set to NULL; otherwise, the recognizer context's WordList property is set to the InkWordList that was created in the OnCreate method. Finally, the InkStrokes of the ink collector is reattached to the recognizer context, the recognizer context's BackgroundRecognizeWithAlternates method is called, and the menu is updated.

The window's OnFactoid method handles the factoid commands on the Factoid menu. It first sets the recognizer context's Strokes property to NULL, sets the recognizer context's Factoid property to the selected factoid, and reassigns the InkStrokes of the ink collector to the recognizer context. If the Factoid object is supported by the recognizer context, the recognizer context's BackgroundRecognizeWithAlternates method is called; otherwise, an error message is displayed. Finally, the menu and status bar are updated.

The window's OnGuide method handles the commands on the Guide menu. If the recognizer context supports the guide options, the OnGuide method sets the recognizer context's Strokes property to NULL, sets the recognizer context's Guide property to the selected guide setting, reassigns the InkStrokes of the ink collector to the recognizer context, and calls the recognizer context's BackgroundRecognizeWithAlternates method. Otherwise, an error message is displayed. Finally, the input window, menu, and status bar are updated.

The window's OnMode method handles the commands on the Mode menu. It disables the ink collector, updates the ink collector's CollectionMode property, updates the menu, and shows or hides the gesture lists. Finally, the ink collector is enabled.

The window's OnRecognize method handles the Recognize command on the Ink menu. It calls the recognizer context's EndInkInput method to keep ink from being added to the recognizer context. This is sometimes necessary, as not all recognizers support partial recognition. Then it calls the recognizer context's Recognize method, and passes the results to the window's OnRecognitionWithAlternates method. Finally, the InkStrokes of the ink collector is reassigned to the recognizer context.

The window's OnClear method handles the Clear command on the Ink menu. It deletes the strokes from the ink collector's Ink property, releases the old strokes collection and creates a new one for the ink collector's Ink property, and attaches the new strokes collection to the recognizer context.

The window's OnExit method handles the Exit command on the Ink menu, and raises the WM_CLOSE event.

Helper Methods

The window's LoadMenu method is called from the window's Run method, and adds the list of supported recognizers and the list of supported factoids to the menu. First, it retrieves the InkRecognizers. Then it iterates through the available recognizers and only selects ones that have a list of languages in the Languages property, which it adds to the Recognizer menu. Finally, it populates the Factoid menu with the list of factoids defined as a global constant.

The window's UseRecognizer method is called from the window's OnRecognizer method when the user selects a new recognizer. It creates a recognizer context, detaches the old context from the recognizer event sink, clears and releases the old context, and attaches the new context to the recognizer event sink.

Then, the UseRecognizer method checks the recognizer's Capabilities property, which returns an InkRecognizerCapabilities value. If the recognizer supports lined input, the Lines command on the Guide menu is enabled. If the recognizer supports boxed input, the Boxes command is enabled. If the recognizer does not support free input, the None command is disabled. If the current guide selection is not supported, both the Guide property of the recognizer context and the menu are updated.

Then, the UseRecognizer method attempts to set the WordList and Factoid properties of the recognizer context. If either setting is not supported by the recognizer, then the default value is used and the menu is updated.

Finally, the UseRecognizer method attaches the Strokes property of the ink collector's InkDisp object to the recognizer context, changes the output window's font to one supported by the language of the recognizer, resets the output window, and updates the recognition results by calling the recognizer context's BackgroundRecognizeWithAlternates method.

The window's GetGestureName method is called from the window's OnGesture method. It searches for the gesture and returns an index to the gesture's name, which is stored in a string table in the AdvReco.rc file.