Windows Presentation Foundation

Take Snapshots of Videos with WPF

With WPF's Imaging-Classes you can take snapshots of any Visual. The snapshot can be saved in any common Image-Format, like e.g. JPG. Let's take a look at a pretty short example, that shows how easy this can be done. The example takes snapshots of a Video. The following Window contains a MediaElement and a Button. The MediaElement plays the Video thomasOnBoard.wmv. The Button defines an Eventhandler for the Click-Event. It takes a snapshot of the video, when you click it.
<Window x:Class="SnapShots.Window1"
    xmlns=http://schemas.microsoft.com/winfx/2006/xaml/...
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300"

 ResizeMode="NoResize">
  <StackPanel>
   <MediaElement x:Name="media" Height="200" Stretch="Fill">
      <MediaElement.Triggers>
       <EventTrigger RoutedEvent="MediaElement.Loaded">
        <BeginStoryboard>
         <Storyboard>
          <MediaTimeline
Source="thomasOnBoard.wmv"
           RepeatBehavior="Forever"/>
         </Storyboard>
        </BeginStoryboard>
       </EventTrigger>
      </MediaElement.Triggers>
     </MediaElement>
     <Button Click="Button_Click" Content="Snapshot"/>
  </StackPanel>
</Window>
Let's look at the Eventhandler of the Button. An instance of the RenderTargetBitmap-class is created with some parameters about image-size, dots per inch (dpi) and Pixelformat. The Render-Method gets the MediaElement as a parameter, so MediaElements visual appearance is stored in the RenderTargetBitmap in memory. With a JpegBitmapEncoder and a FileStream the Image is written as a JPG to disk. That's it.
void Button_Click(object sender, RoutedEventArgs e)
{
  Size dpi = new Size(96,96);
  RenderTargetBitmap bmp = 
    new RenderTargetBitmap(300, 200, 
      dpi.Width, dpi.Height, PixelFormats.Pbgra32);
  bmp.Render(media);

  JpegBitmapEncoder encoder = new JpegBitmapEncoder();
  encoder.Frames.Add(BitmapFrame.Create(bmp));

  string filename = Guid.NewGuid().ToString()+".jpg";
  FileStream fs = new FileStream(filename,FileMode.Create);
  encoder.Save(fs);
  fs.Close();

  Process.Start(filename);
}
Instead of taking the picture in the Button_Click eventhandler, you could create a Timer and take an Image every 0.1s. That allows you to extract an image-sequence of your videos. As it works for any Visual, and everything that's on the screen in a WPF-Application is a visual, there are many things you can do with it. You could create a snapshot of an Image drawn to an inkCanvas, upload it to a webserver to display it on a webpage etc.
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Built-in DataGrid for WPF is planned

Yes, they are planning to release it. Really great news. Today there's no DataGrid for WPF-applications as part of .NET Framework 3.5. There are only third-party controls like the Grid from Xceed or Infragistics. Have you ever built a business application without a DataGrid? I haven't. I'm really happy to hear that microsoft will release a DataGrid for WPF as part of .NET. That wouldn't make thirdparty-components necessary (If you don't need all functionality e.g. Infragistics provides). I hope the DataGrid for WPF will be more like the DataGridView of WinForms in NET 2.0, and not like DataGrid in .NET < 2.0. :-) Take a look at the .NET 3.5 roadmap on Scott Guthries blogpost. There's a little line containing this information about a planned built-in DataGrid by end 2008. Also some other missing controls are planned, like Calendar/DatePicker.
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TechEd Developers 2007 in retrospect – Monday

Last week I went to Barcelona for five days, participating at TechEd Developers 2007 (05. - 09. november). In the following posts I'll just show you a short summary of my experience at TechEd Developers 2007. Let's start on Monday. On Monday the Keynote-Session started after a life grafiti-show with some really breaking news presented by S. Somasegar (Microsofts Corporate Vice President of the developer division):
  • Visual Studio 2008 and .NET 3.5 will be available to MSDN subscribers by the end of November
  • The first CTP of Microsofts Sync Framework is available now
  • For those of you using Microsoft Popfly, a new Popfly Explorer will be available
  • This year there will already be a CTP of the next Version of Visual Studio, called "Rosario". In 2008 there will be a Beta of it
That are great news, especially the release of Visual Studio 2008 before the end of November. In fact Visual Studio 2008 really differs from the Visual Studio versions we had before. It's the first time you can build applications that target different Framework Versions. With Visual Studio 2008 you can build applications that target .NET 2.0, .NET 3.0 or even .NET 3.5. This feature is called Multi-Targeting, and its possible, because .NET 2.0, .NET 3.0 and .NET 3.5 are all using the same Common Language Runtime, the CLR 2.0 that was introduced with .NET 2.0. Of course another great feature is the possibility to debug into the .NET Framework source code. A great possibility to learn some new best practices and to look how Microsoft has done it The Microsoft Sync Framework is a new platform for enabling roaming, offline and collaboration across your applications, services and devices. The Framework also contains built-in support for synchronizing relational databases, NTFS and FAT file systems, etc. Get some more infos and the first CTP of it here. After the Keynote-Session I joined the Session A Tour of Visual Studio 2008 and the .NET Framework 3.5, speaker Daniel Moth. Daniel explained that the .NET Framework 3.5 is a superset of .NET 3.0 (and so still uses the CLR 2.0). He showed some great features of the new IDE, like the new refactoring features added to the contextmenu in the codeeditor, or the transparency-feature for the intellisense-Window. You can make the intellisense-Window transparent by pressing the Ctrl-Key. So you can look at your code while leaving the intellisense-window open. Daniel also explained the terms of the green and red bits in a really good manner. Green bits are those assemblies that are new in .NET 3.5, and haven't existed in .NET 3.0. Red bits are those assemblies that already existed in .NET 3.0, but are lightly extended and fixed with an installation of .NET 3.5. The Red bits are called "red", because they describe a difficulty. If your .NET 3.0 application takes advantage of a not well implemented feature (maybe call it a bug :-)) in .NET 3.0 and that bug will be fixed with .NET 3.5, your application won't work correctly anymore when you change this bug/feature by installing .NET 3.5. So microsoft has to be very careful with the red bits that are shipped as part of .NET 3.5. From the green and red bits you could also conclude something about the installation of .NET 3.5:
  • If you have .NET 3.0 already installed, an installation of .NET 3.5 will use this existing installation and change the red bit assemblies (some existing .NET 3.0 assemblies) and add some brand new Assemblies (the green bits). That means, after the installation of .NET 3.5 you wont come back to .NET 3.0, but every .NET 3.0 application should run well on .NET 3.5 (if Microsoft has done a good job with the red bits)
  • If you haven't .NET 3.0 installed, an installation of .NET 3.5 will install whole .NET 3.0, plus the red and green bits of .NET 3.5
As the last session on Monday, I joined the session A Windows Communication Foundation (WCF) Walkthrough using Visual Studio 2008, but it wasn't really as amazing as I thought before. The only new stuff for me about WCF I got out of this session were the things that ship with Visual Studio 2008, but nothing about WCF itself. In Visual Studio 2008 there will be new Project-Templates to generate a WCF-Library and a new UI that allows you to test your services easily. In the evening, the "Ask The Experts" was open. The first thing I was looking for was an "Ask The Experts to WPF"-stand. But I didn't find one. There were stands with experts in Visual Studio 2008, SQL Server, BI, Office, Silverlight and Expression and many more, but no stand with experts in WPF. So I just went to the Silverlight stand and asked for the WPF stand. The guy pointed to another person and said: "He asked me exactly the same questions 10 seconds ago, unfortunately there is no stand with WPF-experts". And the other person said, "Some questions about WPF?". Yeah, I thought, here I was right. Looking at his name, I recognized the name of the person and I knew, here I'm really right. It was Ian Griffiths, author of the very first WPF-book, "Programming WPF", currently in its second edition. We spoke about nearly 1 hour about developing real enterprise applications with WPF, about the WPF-Designer in Visual Studio and about using Blend for designing your app. In most cases, Ian and I had the same opinion, and we both are waiting for the datagrid as part of .NET/WPF. :-) Today there are only third-party-grids available from famous control authors like those from Infragistics. Even in .NET 3.5 and WPF 3.5 (it's really called WPF 3.5 and not WPF 1.5), Microsoft introduced no more 2D-Controls. But WPF 3.5 contains some new 3D-Elements like UIElement3D or Viewport2DVisual3D, that receive Input Events and make interactive 3D much easier than in WPF 3.0.
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