How to convert ink strokes to text (Windows Runtime apps using JavaScript and HTML)

Applies to Windows only

Learn how to use handwriting recognition and convert ink strokes to text in a Windows Store app using JavaScript.

Updates for Windows 8.1:  Windows 8.1 introduces a number of updates and improvements to the pointer input APIs. See API changes for Windows 8.1 for more info.

For this example, we use the built-in recognition functionality (RecognizeAsync) of the InkManager object to convert all ink strokes to text and store the results in the manager.

If recognition is not required, use an InkStrokeContainer object instead of an InkManager. Previous recognition results are still available through GetRecognitionResults.

If only recognition is required, and not storage, use an InkRecognizerContainer instead of an InkManager.

What you need to know

Technologies

Prerequisites

This how-to builds on Quickstart: Capturing ink data.

We assume that you can create a basic Windows Store app using JavaScript that uses the Windows Library for JavaScript template.

Instructions

Step 1: Create an ink manager

Initialize an InkManager object that will process and manipulate the ink-related data obtained from the pointer input.


        // Create an ink manager.
        // InkManager is documented at http://go.microsoft.com/fwlink/?LinkID=260648.
        var inkManager = new Windows.UI.Input.Inking.InkManager();


Step 2: Set a default language for recognition

Set the default recognizer language. For Windows 8, each language pack includes a set of relevant recognition languages. For more info on the valid recognition languages, see Name.

If you do not set the default language, the system selects one based on the primary language identified in the Language control panel. If the primary language does not include a recognition language, the system uses one of the secondary languages or EN-US.

Note  

Here's how to set the default language to Microsoft English (US) Handwriting Recognizer.


// Set default recognition language.
if (!setRecognizerByName("Microsoft English (US) Handwriting Recognizer")) {
    statusMessage.innerText += "\nRecognition: Failed to find English (US) recognizer.";
}
else {
    statusMessage.innerText += "\nRecognition: English (US) recognizer.";
}


Use GetRecognizers to retrieve the available recognition languages on the user's system. Iterate through this list and, if the desired language is found, call SetDefaultRecognizer. If the desired language is not found, display an error and use the system default instead.


/// <summary>
/// Finds a specific recognizer, and sets the inkManager's default to that recognizer.
/// Returns true if successful.
/// </summary>
/// <param name="recognizerName">The name of the handwriting recognizer.</param>
function setRecognizerByName(recognizerName) {
    try {
        // recognizers is a normal JavaScript array
        var recognizers = inkManager.getRecognizers();
        for (var i = 0, len = recognizers.length; i < len; i++) {
            if (recognizerName === recognizers[i].name) {
                inkManager.setDefaultRecognizer(recognizers[i]);
                return true;
            }
        }
    }
    catch (e) {
        displayError("setRecognizerByName: " + e.toString());
    }
    return false;
}


Step 3: Enable recognition

Provide a way for your user to initiate recognition.

First, declare a set of mode buttons.


<body>
<div id="applicationTitle">Ink sample</div>
<div>
    <canvas id="inkCanvas"></canvas>
    <div>
        <button id="load">Load</button>
        <button id="save">Save</button>
        <button id="draw">Draw</button>
        <button id="select">Select</button>
        <button id="selectall">Select all</button>
        <button id="erase">Erase</button>
        <button id="eraseAll">Erase all</button>
        <button id="recognize" value="selected">Handwriting recognition</button>
    </div>
</div>
<div id="modeMessage"></div>
<div id="deviceMessage"></div>
<div id="statusMessage"></div>
</body>


Then, declare an event listener.


get("recognize").addEventListener("click", recognizeStrokes, false);


Step 4: Process all strokes

Finally, you handle the recognition request and process all strokes managed by the ink manager through the recognition engine.

For simplicity, this example processes all strokes by specifying an InkRecognitionTarget of all. Specifying an InkRecognitionTarget of recent processes only the strokes that were added since the last call to RecognizeAsync. This is typically useful in cases where all strokes are treated as handwriting, and they need to be recognized dynamically based on an event such as pointerup, instead of a user command. Use selected to process only selected strokes.


/// <summary>
/// Invoked when the "Handwriting recognition" button is pressed.
/// The ink manager processes all strokes through recognizeAsync, which returns 
/// the number of words detected and a set of recognition results for each word. 
/// </summary>
/// <param name="evt">The event object.</param>
function recognizeStrokes(evt) {

    // Ensure ink strokes exist before calling recognizeAsync.
    if (inkManager.getStrokes().length > 0) {
        // recognizeAsync fails if other recognition tasks are in progress.
        try {
            // The ink manager is used to store the recognition results.
            // recognizeAsync has 3 modes: all | selected | recent.
            // For this example, we process all strokes.
            // recognizeAsync is documented at http://go.microsoft.com/fwlink/?LinkID=265172.
            inkManager.recognizeAsync(Windows.UI.Input.Inking.InkRecognitionTarget.all).done
            (
                // The recognitionResult object returned by recognizeAsync exposes the 
                // bounding rect, strokes, and text candidates for each word. 
                // In this example, we simply display the word count and recognition results.
                function (results) {
                    // recognizeAsync does not automatically update existing recognition results in the ink manager.
                    // updateRecognitionResults is documented at http://go.microsoft.com/fwlink/?LinkID=265175.
                    inkManager.updateRecognitionResults(results);

                    var x = inkManager.getRecognizers();

                    // Display the number of words returned in results.
                    statusMessage.innerText = "Words recognized: " + results.length.toString();

                    // Iterate through each word and display the ranked list of possible matches.
                    for (var i = 0; i < results.length; i++) {
                        statusMessage.innerText += "\nWord" + (i+1).toString() + ":";
                        var alts = results[i].getTextCandidates();
                        for (var j = 0; j < alts.length; j++) {
                            statusMessage.innerText += " " + alts[j].toString();
                        }
                    }
                },
                function (e) {
                    displayError("InkManager::recognizeAsync: " + e.toString());
                }
            );
        }
        catch (e) {
            displayError("recognize: " + e.toString());
        }
    }
    else {
        statusMessage.innerText = "No strokes to recognize.";
    }
}


See the Input: ink sample for an example of how to use the bounding rect and text candidates for each word that are exposed through the collection of InkRecognitionResult objects returned by RecognizeAsync. After recognition has completed, tap a word to display a list of selectable text candidates in a flyout adjacent to the word.

Complete example


//// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
//// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
//// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
//// PARTICULAR PURPOSE.
////
//// Copyright (c) Microsoft Corporation. All rights reserved

// Windows Store app that demonstrates the use of the Windows.UI.Input.Inking APIs.

// Ink functionality is documented at http://go.microsoft.com/fwlink/?LinkID=260649.
// User interaction functionality is documented at http://go.microsoft.com/fwlink/?LinkID=260650.
// Ink APIs are documented at http://go.microsoft.com/fwlink/?LinkID=260652.
// Pointer APIs are documented at http://go.microsoft.com/fwlink/?LinkID=260653.

(function ()
{
    "use strict";

    //
    // Global variables
    //

        // UI object references.
        var inkCanvas;
        var inkContext;
        var modeMessage;
        var deviceMessage
        var statusMessage;

        // Create an ink manager.
        // InkManager is documented at http://go.microsoft.com/fwlink/?LinkID=260648.
        var inkManager = new Windows.UI.Input.Inking.InkManager();

        // Initial pointer values.
        var pointerId = -1;
        var pointerDeviceType = null;

        // Initial stroke property values.
        var strokeColor;
        var strokeWidth;

    //
    // End global variables
    //

    // Obtain reference to the specified element.
    function get(elementId)
    {
        return document.getElementById(elementId);
    }

    function initialize()
    {
        // Set up the UI.
        inkCanvas = get("inkCanvas");
        inkContext = inkCanvas.getContext("2d");

        inkContext.lineCap = "round";
        inkContext.lineKJoin = "round";

        inkCanvas.width = window.innerWidth - 10;
        inkCanvas.height = window.innerHeight * 0.5;

        deviceMessage = get("deviceMessage");
        deviceMessage.innerText = "Undefined";
        modeMessage = get("modeMessage");
        modeMessage.innerText = inkManager.mode;
        statusMessage = get("statusMessage");
        statusMessage.innerText = "No pointer input detected."

        // Set initial ink mode.
        drawStrokes();

        // Set default recognition language.
        if (!setRecognizerByName("Microsoft English (US) Handwriting Recognizer")) {
            statusMessage.innerText += "\nRecognition: Failed to find English (US) recognizer.";
        }
        else {
            statusMessage.innerText += "\nRecognition: English (US) recognizer.";
        }

        // Set up the handlers for input processing.
        inkCanvas.addEventListener("pointerdown", onPointerDown, false);
        inkCanvas.addEventListener("pointermove", onPointerMove, false);
        inkCanvas.addEventListener("pointerup", onPointerUp, false);

        get("save").addEventListener("click", saveStrokes, false);
        get("load").addEventListener("click", loadStrokes, false);
        get("draw").addEventListener("click", drawStrokes, false);
        get("select").addEventListener("click", selectStrokes, false);
        get("selectall").addEventListener("click", selectAllStrokes, false);
        get("erase").addEventListener("click", eraseStrokes, false);
        get("eraseAll").addEventListener("click", eraseAllStrokes, false);
        get("recognize").addEventListener("click", recognizeStrokes, false);
    }
    document.addEventListener("DOMContentLoaded", initialize, false);

    function getPointerDeviceType(pId)
    {
        var pointerDeviceType;
        var pointerPoint = Windows.UI.Input.PointerPoint.getCurrentPoint(pId);
        switch (pointerPoint.pointerDevice.pointerDeviceType)
        {
            case Windows.Devices.Input.PointerDeviceType.touch:
                pointerDeviceType = "Touch";
                break;

            case Windows.Devices.Input.PointerDeviceType.pen:
                pointerDeviceType = "Pen";
                break;

            case Windows.Devices.Input.PointerDeviceType.mouse:
                pointerDeviceType = "Mouse";
                break;
            default:
                pointerDeviceType = "Undefined";
        }
        deviceMessage.innerText = pointerDeviceType;
        return pointerDeviceType;
    }

    // Occurs when the pointer (touch, pen, mouse) is detected by the canvas.
    // Each stroke begins with onPointerDown.
    function onPointerDown(evt)
    {
        // Get the device type for the pointer input.
        pointerDeviceType = getPointerDeviceType(evt.pointerId);

        // Process pen and mouse (with left button) only. Reserve touch for manipulations.
        if ((pointerDeviceType === "Pen") || ((pointerDeviceType === "Mouse") && (evt.button === 0)))
        {
            statusMessage.innerText = pointerDeviceType + " pointer down: Start stroke. "

            // Process one pointer at a time.
            if (pointerId === -1)
            {
                var current = evt.currentPoint;

                // Start drawing the stroke.
                inkContext.beginPath();
                inkContext.lineWidth = strokeWidth;
                inkContext.strokeStyle = strokeColor;

                inkContext.moveTo(current.position.x, current.position.y);

                // Add current pointer to the ink manager (begin stroke).
                inkManager.processPointerDown(current);

                // The pointer id is used to restrict input processing to the current stroke.
                pointerId = evt.pointerId;
            }
        }
        else
        {
            // Process touch input.
        }
    }

    // Mouse: Occurs when the pointer moves.
    // Pen/Touch: Occurs at a steady rate (approx. 100 messages/second) whether the pointer moves or not.
    function onPointerMove(evt)
    {
        // Process pen and mouse (with left button) only. Reserve touch for manipulations.
        if ((pointerDeviceType === "Pen") || ((pointerDeviceType === "Mouse") && (evt.button === -1)))
        {
            statusMessage.innerText = pointerDeviceType + " pointer move: Draw stroke as lines. "
            // The pointer Id is used to restrict input processing to the current stroke.
            // pointerId is updated in onPointerDown().
            if (evt.pointerId === pointerId)
            {
                var current = evt.currentPoint;

                // Draw stroke in real time.
                inkContext.lineTo(current.rawPosition.x, current.rawPosition.y);
                inkContext.stroke();

                // Add current pointer to the ink manager (update stroke).
                inkManager.processPointerUpdate(current);
            }
        }
        else
        {
            // Process touch input.
        }
    }

    // Occurs when the pointer (touch, pen, mouse) is lifted from the canvas.
    // Each stroke ends with onPointerUp.
    function onPointerUp(evt)
    {
        // Process pen and mouse (with left button) only. Reserve touch for manipulations.
        if ((pointerDeviceType === "Pen") || ((pointerDeviceType === "Mouse") && (evt.button === 0)))
        {
            statusMessage.innerText = pointerDeviceType + " pointer up: Finish stroke. "
            if (evt.pointerId === pointerId) {
                // Add current pointer to the ink manager (end stroke).
                inkManager.processPointerUp(evt.currentPoint);

                // End live drawing.
                inkContext.closePath();

                // Render strokes using bezier curves.
                renderAllStrokes();

                // Reset pointer Id.
                pointerId = -1;
            }
        }
        else
        {
            // Process touch input.
        }
    }

    // Render all strokes using bezier curves instead of line segments.
    function renderAllStrokes()
    {
        statusMessage.innerText += "Render strokes as bezier curves."

        // Clear the drawing surface of existing strokes.
        inkContext.clearRect(0, 0, inkCanvas.width, inkCanvas.height);

        // Iterate through each stroke.
        inkManager.getStrokes().forEach(
            function (stroke)
            {
                inkContext.beginPath();
                if (stroke.selected) {
                    inkContext.lineWidth = stroke.drawingAttributes.size.width * 2;
                    inkContext.strokeStyle = "green";
                } else {
                    inkContext.lineWidth = stroke.drawingAttributes.size.width;
                    inkContext.strokeStyle = "black";
                }

                // Enumerate through each line segment of the stroke.
                var first = true;

                stroke.getRenderingSegments().forEach(
                    function (segment)
                    {
                        // Move to the starting screen location of the stroke.
                        if (first)
                        {
                            inkContext.moveTo(segment.position.x, segment.position.y);
                            first = false;
                        }
                        // Calculate the bezier curve for the segment.
                        else
                        {
                            inkContext.bezierCurveTo(segment.bezierControlPoint1.x,
                                                     segment.bezierControlPoint1.y,
                                                     segment.bezierControlPoint2.x,
                                                     segment.bezierControlPoint2.y,
                                                     segment.position.x, segment.position.y);
                        }
                    }
                );
                
                // Draw the stroke.
                inkContext.stroke();
                inkContext.closePath();
            }
        );
    }

    // Set up draw mode.
    function drawStrokes() {
        inkManager.mode = Windows.UI.Input.Inking.InkManipulationMode.inking;
        strokeColor = "black";
        strokeWidth = 2;
        modeMessage.innerText = inkManager.mode;
    }

    // Set up selection mode.
    function selectStrokes() {
        inkManager.mode = Windows.UI.Input.Inking.InkManipulationMode.selecting;
        strokeColor = "red";
        strokeWidth = 1;
        modeMessage.innerText = inkManager.mode;
    }

    // Set up erase mode.
    function eraseStrokes() {
        inkManager.mode = Windows.UI.Input.Inking.InkManipulationMode.erasing;
        strokeColor = "gold";
        strokeWidth = 1;
        modeMessage.innerText = inkManager.mode;
    }

    // Select all strokes handler.
    function selectAllStrokes() {
        inkManager.mode = Windows.UI.Input.Inking.InkManipulationMode.selecting;
        strokeColor = "red";
        strokeWidth = 1;
        modeMessage.innerText = "Select all strokes.";
        // Iterate through each stroke.
        inkManager.getStrokes().forEach(
            function (stroke) {
                stroke.selected = 1;
            }
            );
        renderAllStrokes();
    }

    // Select all strokes handler.
    function eraseAllStrokes() {
        inkManager.mode = Windows.UI.Input.Inking.InkManipulationMode.inking;
        strokeColor = "black";
        strokeWidth = 2;
        modeMessage.innerText = "Erase all strokes.";
        // Iterate through each stroke.
        inkManager.getStrokes().forEach(
            function (stroke) {
                stroke.selected = 1;
            }
            );
        inkManager.deleteSelected();
        renderAllStrokes();
    }

    // Save all strokes owned by inkManager.
    function saveStrokes()
    {
        // Ensure that strokes exist before calling saveAsync.
        if (inkManager.getStrokes().size > 0)
        {
            // Set up the file save screen.
            var savePicker = Windows.Storage.Pickers.FileSavePicker();
            savePicker.suggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.picturesLibrary;
            savePicker.fileTypeChoices.insert("GIF with embedded ISF", [".gif"]);
            savePicker.defaultFileExtension = ".gif";

            // Set up the stream.
            var saveStream = null;

            // Asynchronously save the ink data to the stream.
            savePicker.pickSaveFileAsync().done(
            function (file)
            {
                if (null !== file)
                {
                    file.openAsync(Windows.Storage.FileAccessMode.readWrite).then(
                        function (stream)
                        {
                            saveStream = stream;
                            return inkManager.saveAsync(saveStream);
                        }
                    ).then(
                        function ()
                        {
                            return saveStream.flushAsync(); 
                        },
                        function (e) {
                            // Override the standard saveAsync error with our own.
                            throw new Error("saveAsync");
                        }
                    ).done(
                        function ()
                        {
                            statusMessage.innerText = "Strokes saved as GIF with embedded ISF (.gif).";
                            saveStream.close();
                        },
                        function (e) {
                            statusMessage.innerText = "Save: " + e.toString();
                            // Close the stream if open.
                            if (saveStream) {
                                saveStream.close();
                            }
                        }
                    );
                }
            }
        );
        }
        else
        {
            statusMessage.innerText = "No strokes to save.";
        }
    }

    // Load strokes into an inkManager.
    function loadStrokes()
    {
        // Set up the file open screen.
        var openPicker = Windows.Storage.Pickers.FileOpenPicker();
        openPicker.suggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.picturesLibrary;
        openPicker.fileTypeFilter.replaceAll([".gif"]);

        // Set up the stream.
        var loadStream = null;

        // Asynchronously load the ink data from the stream.
        openPicker.pickSingleFileAsync().done(
            function (file)
            {
                if (null != file)
                {
                    file.openAsync(Windows.Storage.FileAccessMode.read).then(
                        function (stream) {
                            loadStream = stream;
                            return inkManager.loadAsync(loadStream);
                        }).done(
                            function()
                            {
                                var strokes = inkManager.getStrokes().length;
                                if (strokes === 0)
                                {
                                    statusMessage.innerText = "No strokes in file.";
                                }
                                else
                                {
                                    statusMessage.innerText = strokes + " strokes loaded.";
                                }
                                renderAllStrokes();
                                loadStream.close();
                            },
                            function (e)
                            {
                                statusMessage.innerText = "Load failed.";
                                if (loadStream)
                                {
                                    // Close the stream if open.
                                    loadStream.close();
                                }
                            });
                }
            });
    }

    /// <summary>
    /// Finds a specific recognizer, and sets the inkManager's default to that recognizer.
    /// Returns true if successful.
    /// </summary>
    /// <param name="recognizerName">The name of the handwriting recognizer.</param>
    function setRecognizerByName(recognizerName) {
        try {
            // recognizers is a normal JavaScript array
            var recognizers = inkManager.getRecognizers();
            for (var i = 0, len = recognizers.length; i < len; i++) {
                if (recognizerName === recognizers[i].name) {
                    inkManager.setDefaultRecognizer(recognizers[i]);
                    return true;
                }
            }
        }
        catch (e) {
            displayError("setRecognizerByName: " + e.toString());
        }
        return false;
    }

    /// <summary>
    /// Invoked when the "Handwriting recognition" button is pressed.
    /// The ink manager processes all strokes through recognizeAsync, which returns 
    /// the number of words detected and a set of recognition results for each word. 
    /// </summary>
    /// <param name="evt">The event object.</param>
    function recognizeStrokes(evt) {

        // Ensure ink strokes exist before calling recognizeAsync.
        if (inkManager.getStrokes().length > 0) {
            // recognizeAsync fails if other recognition tasks are in progress.
            try {
                // The ink manager is used to store the recognition results.
                // recognizeAsync has 3 modes: all | selected | recent.
                // For this example, we process all strokes.
                // recognizeAsync is documented at http://go.microsoft.com/fwlink/?LinkID=265172.
                inkManager.recognizeAsync(Windows.UI.Input.Inking.InkRecognitionTarget.all).done
                (
                    // The recognitionResult object returned by recognizeAsync exposes the 
                    // bounding rect, strokes, and text candidates for each word. 
                    // In this example, we simply display the word count and recognition results.
                    function (results) {
                        // recognizeAsync does not automatically update existing recognition results in the ink manager.
                        // updateRecognitionResults is documented at http://go.microsoft.com/fwlink/?LinkID=265175.
                        inkManager.updateRecognitionResults(results);

                        var x = inkManager.getRecognizers();

                        // Display the number of words returned in results.
                        statusMessage.innerText = "Words recognized: " + results.length.toString();

                        // Iterate through each word and display the ranked list of possible matches.
                        for (var i = 0; i < results.length; i++) {
                            statusMessage.innerText += "\nWord" + (i+1).toString() + ":";
                            var alts = results[i].getTextCandidates();
                            for (var j = 0; j < alts.length; j++) {
                                statusMessage.innerText += " " + alts[j].toString();
                            }
                        }
                    },
                    function (e) {
                        displayError("InkManager::recognizeAsync: " + e.toString());
                    }
                );
            }
            catch (e) {
                displayError("recognize: " + e.toString());
            }
        }
        else {
            statusMessage.innerText = "No strokes to recognize.";
        }
    }

    // Returns true if any strokes inside the ink manager are selected; false otherwise.
    function anySelected() {
        var strokes = inkManager.getStrokes();
        var len = strokes.length;
        for (var i = 0; i < len; i++) {
            if (strokes[i].selected) {
                return true;
            }
        }
        return false;
    }



})();


Related topics

Conceptual
Responding to pen and stylus input
Quickstart: Capturing ink data
Reference
Windows.Devices.Input
Windows.UI.Core
Windows.UI.Input
Windows.UI.Input.Inking
Samples (DOM)
Input: DOM pointer event handling sample
Samples (Windows Store app APIs)
Input: Device capabilities sample
Input: Ink sample
Input: Simplified ink sample

 

 

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