Stefan Wick's Weblog - Development with Silverlight, WPF and Tablet PC : Windows Presentation Foundation

Rendering ink and image to a bitmap using WPF

swick — Sun, 02 Dec 2007 08:21:00 GMT

To follow-up on my previous blog post and to complete the story about rendering ink onto pictures and saving the results as a bitmap file, I want to show how this is done in WPF.

In WPF all rendering uses the pipeline - pictures, videos, ink, text, all gets rendered via WPF's 'Media Integration Layer'. As a result, it's very easy and straightforward to combine rendering these different types, both on screen and on a bitmap.

I have attached a WPF sample app that demonstrates how to collect ink on top of an image and then save the combined visual to a bitmap file. In fact, I have used this sample to create the sample picture that is included in my previous post about doing this in Winforms. Here is a screenshot of the sample app (btw, the ink color picker is borrowed from the InkColorPicker SDK sample).

The key class to accomplish our job in WPF is the RenderTargetBitmap class. Here is the relevant code snippet from the sample app:

// render InkCanvas' visual tree to the RenderTargetBitmap

RenderTargetBitmap targetBitmap =

new RenderTargetBitmap((int)inkCanvas1.ActualWidth,

(int)inkCanvas1.ActualHeight,

96d, 96d,

PixelFormats.Default);

targetBitmap.Render(inkCanvas1);

// add the RenderTargetBitmap to a Bitmapencoder

BmpBitmapEncoder encoder = new BmpBitmapEncoder();

encoder.Frames.Add(BitmapFrame.Create(targetBitmap));

// save file to disk

FileStream fs = File.Open(fileName, FileMode.OpenOrCreate);

encoder.Save(fs);

Unlike the Winforms API, there is no behavioral difference between Windows Vista and Windows XP.

Fun with Ink & XAML Part3: Ink Data Binding

swick — Sat, 03 Nov 2007 16:18:00 GMT

Data binding in WPF provides a great way for applications to present and interact with data. Elements can be bound to data from a variety of data sources - for example XML files. I have put together a sample that uses data binding to retrieve a collection of handwritten ink documents from a data store (XML file), present it to the user and let the user interact with it. As always in this series, the task is accomplished by markup only - no code behind required. The sample markup (and the data file) is attached to this post.

Let's take a look at the sample markup, specifically what's inside the <Grid.Resources> tag. I have highlighted the sections that are relevant for the data binding:

<Grid.Resources>

<TextBlock HorizontalAlignment="Center" Foreground="Red"

Text="{Binding XPath=@FileName}"/>

<InkPresenter HorizontalAlignment="Center"

LayoutTransform="0.2,0,0,0.2,0,0">

<InkPresenter.Strokes>

</InkPresenter.Strokes>

</InkPresenter>

</StackPanel>

</DataTemplate>

</Grid.Resources>

The first item here is the XmlDataProvider. This class facilitates the access to XML data for data binding. The other item, our DataTemplate, defines how the data is being presented: The 'FileName' value gets assigned to a <TextBlock/> and the 'Strokes' value gets assigned to the Strokes property of an <InkPresenter/>.

To see how these two resources are being used in the actual UI markup, let's inspect the ListBox element. The ListBox is being used to display a thumbnail view of all ink documents in the data store and to let the user choose which document they want to view or edit.

<ListBox Name="lbStrokes" Background="AntiqueWhite"

ItemsSource="{Binding Source={StaticResource InkData},

XPath=InkFile}"

ItemTemplate="{StaticResource InkDataTemplate}"/>

Now to view and interact with the selected item from our ListBox, we are adding a larger InkCanvas element that is data-bound to the ListBox. So when the user selects a new ink note from the list, that document gets loaded into the InkCanvas automatically. Here is the relevant markup to set up that binding:

<InkCanvas DataContext="{Binding ElementName=lbStrokes,Path=SelectedItem}"

Strokes="{Binding XPath=@Strokes}"

Background="Snow">

Below is a screenshot of the sample that is attached to this post. To run it, unpack the .zip file and load the .xaml file into XamlPad - or just double-click it to open it in IE. Note that the data file (InkData.xml) must reside in the same location as the XAML file.

Next post in this series: Fun with Ink & XAML Part4: WPF BitmapEffects applied to Ink

Previous post in this series: Fun with Ink & Xaml - Part2: Zoom and Scroll

Shape Recognition with WPF and InkAnalysis

swick — Thu, 01 Nov 2007 19:45:00 GMT

Did you know that the Windows Vista SDK contains a shape recognition engine? It's part of the InkAnalysis framework that provides APIs for handwriting recognition, ink parsing and shape recognition. This framework enables some really cool scenarios, especially when combined with WPF. And it's very easy to program against it from a WPF app due to its strongly-typed, WPF-friendly wrapper assembly (iawinfx.dll). Today I want to focus on shapes, I'll work on a seperate post for handwriting recognition (for an overview of InkAnalysis take a look at this MSDN topic).

The sample that comes with this post in the attachment lets the user draw a shape (triangle, ellipse, rectangle, polygon) using the mouse (or stylus if available). The shape reco engine then kicks in and returns the corresponding WPF shape element. Once the shape elements are in the WPF tree, you can use the CheckBoxes to animate or move them around.

One of the key lines in the code is where we tell the InkAnalyzer that our ink stroke should be considered as 'Drawing' (as opposed to handwriting).

inkAnalyzer.SetStrokesType(e.Added, StrokeType.Drawing);

Then, when we get the result nodes from the InkAnalyzer, it will return the actual WPF shape objects, like this:

InkDrawingNode drawingNode = resultNode as InkDrawingNode;

if (drawingNode != null && drawingNode.GetShapeName() != "Other")

{

Shape shapeToAdd = drawingNode.GetShape();

...

}

Here is a screenshot of the sample just before completing the ink stroke:

After MouseUp (or StylusUp), shape recognition kicks in and the WPF shape element gets added to the Canvas.

Now that your handwritten stroke has been converted to a WPF shape, you can utilize the full power of WPF and do fancy things with them. For example: render them with semi-transparent gradients, animate smoothly or move them around - as demonstrated in my sample. The full sample project is attached to this post.

Fun with Ink & Xaml - Part1: Ink Reflections

swick — Thu, 01 Nov 2007 00:44:00 GMT

With the InkCanvas element in WPF you can create stunning inking experiences for TabletPC users (mouse users can play along, too!). Several very cool scenarios can be enabled just by writing markup - without any additional code behind.

Here is a first example: an ink input field (takes input from either stylus or mouse) that has a dynamic reflection effect. While the user is inking, the reflection gets updated dynamically, in real-time. Implemented entirely in markup.

The key feature (besides InkCanvas) here is the VisualBrush. The bottom part of the scene is a Rectangle that gets painted with a VisualBrush that is bound to the ink input control. As a result it gets updated dynamically as the user draws onto the control. Below is the relevant piece of markup. The full XAML file is attached to this post. You can load it into XamlPad to play with it, or just open in IE and ink away.

<Rectangle.Fill>
    <VisualBrush
      Visual="{Binding ElementName=inkBorder}">
      <VisualBrush.RelativeTransform>
        <TransformGroup>
          <ScaleTransform ScaleX="1" ScaleY="-1" />
          <TranslateTransform Y="1" />
        </TransformGroup>
      </VisualBrush.RelativeTransform>
    </VisualBrush>
</Rectangle.Fill>

More information about creating reflections using VisualBrush can be found in this MSDN How-To Topic. Additional How-To topics on Ink in WPF are also available on MSDN.

Next post in this series: Fun with Ink & Xaml - Part2: Zoom and Scroll

.NET 3.5: Viewport2DVisual3D and Ink

swick — Wed, 31 Oct 2007 22:59:00 GMT

WPF 3.5 includes an exciting new feature: Viewport2DVisual3D. It makes building interactive 3D experiences very easy and is nicely integrated with the rest of the WPF Platform. I have used this feature to write a new version of the "Ink Postcard" sample that I wrote a few years back for the Windows SDK. A VS project that contains the new and improved version is attached to this post (you need .NET 3.5 installed to run it).

The sample allows you to draw ink directly onto a 3D model (a Postcard in this case) - even when it is animated! It demonstrates how well this new feature is integrated with things like Ink, Animation, InkCanvas and input from mouse and stylus (when running on a TabletPC).

More information on Viewport2DVisual3D and other great samples around this can be found on Lester's WPF Blog and on Greg Schlechter's Blog.