Digital Ink in WPF

Digital ink used to only be available as part of the Tablet PC SDK. Now it is bundled with Windows Presentation Foundation. This tutorial demonstrates how easy it is to integrate digital ink into your Avalon applications using XAML and VB.
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Originally available only as part of the Tablet PC SDK, digital ink is now integrated into Microsoft's Windows Presentation Foundation.  With the exception of handwriting recognition, Windows programmers can now leverage digital ink in their applications without additional SDKs or runtime libraries.
 
Enabling Ink
 
To enable the collection and display of ink input, developers need only include the InkCanvaselement in their XAML document.

<Window x:Class="WindowsApplication1.Window1"

xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

Title="WindowsApplication1" Width="550" Height="400">

<Grid>

        <InkCanvas />

</Grid>

</Window>

When the above code is compiled, a small black square replaces the mouse cursor when the user hovers over the application window. When the user left-clicks and drags the mouse in the content area, "ink" is invoked and the user is able to draw. 
 
   1.gif
 
Like other tags in XAML, InkCanvas can be used in conjunction with other layout elements and controls. As such, it may be positioned or layered over other elements. The following example displays an image within an InkCanvas

<Window x:Class="WindowsApplication1.Window1"

xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

Title="WindowsApplication1" Width="550" Height="400">

          <Grid>

                    <InkCanvas>

                             <Image Source="http://www.google.com/intl/en/images/logo.gif" />

                    </InkCanvas>

          </Grid>

</Window>

When compiled, the user is able to draw on the image because the graphic is a child of the InkCanvas element.
 
2.gif
 
Controlling Stroke Appearance
 
Using just a bit of C#, it is also possible to control a number of ink properties including stroke color and thickness.  These properties are controlled using the DrawingAttributes class. 
 
Using this class, you can either control the appearance of individual strokes usingStroke.DrawingAttributes or the default appearance of any new stroke collected by the InkCanvas using InkCanvas.DefaultDrawingAttributes.
 
Below is a list of properties supported by the DrawingAttributes class: 

 

Name  Description
Color  Gets or sets the color of a Stroke.
 
FitToCurve  Gets or sets a value that indicates whether Bezier smoothing is used to render the Stroke.
Height  Gets or sets the height of the stylus used to draw the Stroke.
IgnorePressure  Gets or sets a value that indicates whether the thickness of a rendered Stroke changes according the amount of pressure applied.
IsHighlighter  Gets or sets a value that indicates whether the Stroke looks like a highlighter.
StylusTip  Gets or sets the shape of the stylus used to draw the Stroke.
StylusTipTransform  Gets or sets the Matrix that specifies the transformation to perform on the stylus' tip.

 

 Member names and descriptions taken from Microsoft's WinFX SDK

Using a few of the above properties, we can create a simple method for setting the default ink color to blue with a stroke thickness of 2px (2px by 2px).

Private Sub setInkBlue(ByVal sender As ObjectByVal e As RoutedEventArgs)

    ' set the DefaultDrawingAttributes for a blue pen.

    myInkCanvas.DefaultDrawingAttributes.Color = Colors.Blue

    myInkCanvas.DefaultDrawingAttributes.Height = 2

    myInkCanvas.DefaultDrawingAttributes.Width = 2

End Sub

Editing with InkCanvas
 
InkCanvas also comes with a few "freebies".  One of these features is a built-in editing mode, allowing users to select, drag, resize, and erase ink strokes.  
 
There are two main properties available to control editing: InkCanvas.EditingMode andInkCanvas.EditingModeInverted.  The first property controls the tip of the stylus.  The second controls the "eraser".  Both of these properties use InkCanvasEditingMode to specify how stylus input is handled.
 
By default, the EditingMode of InkCanvas is set to Ink while EditingModeInverted is set toEraseByStroke
However, InkCanvasEditingMode supports a number of settings: 
 

Name  Description
EraseByPoint  Indicates that the pen erases part of a stroke when the pen intersects the stroke.
EraseByStroke  Indicates that the pen erases an entire stroke when the pen intersects the stroke
GestureOnly  Indicates that the InkCanvas responds to gestures, and does not receive ink.
Ink  Indicates that ink appears on the InkCanvas when the pen sends data to it.
InkAndGesture  Indicates that the InkCanvas responds to gestures, and receives ink.
None  Indicates that no action is taken when the pen sends data to the InkCanvas.
Select  Indicates that the pen selects strokes and elements on the InkCanvas.

 Names and descriptions taken from Microsoft's WinFX SDK
 
Specifying either Select or EraseByStroke will override this setting providing alternate functionality. The following method sets the editing mode to select:

 

' selection

Private Sub [Select](ByVal sender As ObjectByVal e As RoutedEventArgs) 

    ' set the EditingMode to Select

    myInkCanvas.EditingMode = InkCanvasEditingMode.[Select]

End Sub

When this method is called, the user can select and drag a stroke or group of strokes by either directly clicking on the stroke or 
"lassoing" a group of strokes.
 
3.gif
 
A similar method can be created to set the editing mode to erase:

' erase

Private Sub [Erase](ByVal sender As ObjectByVal e As RoutedEventArgs) 

    ' set the EditingMode to EraseByStroke

    myInkCanvas.EditingMode = InkCanvasEditingMode.EraseByStroke

End Sub

When this method is called, the user can erase ink on the canvas by holding down the left mouse button and moving the cursor (an eraser in this mode) over any stroke.

NOTE: THIS ARTICLE IS CONVERTED FROM C# TO VB.NET USING A CONVERSION TOOL. ORIGINAL ARTICLE CAN BE FOUND ON C# Corner (http://www.c-sharpcorner.com/).

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