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• How to create a widget – Introducing the Piwik Platform

  4 septembre 2014, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to create a scheduled task in Piwik). This time you’ll learn how to create a new widget. For this tutorial you will need to have basic knowledge of PHP.

  What is a widget in Piwik ?

  Widgets can be added to your dashboards or exported via a URL to embed it on any page. Most widgets in Piwik represent a report but a widget can display anything. For instance a RSS feed of your corporate news. If you prefer to have most of your business relevant data in one dashboard why not display the number of offline sales, the latest stock price, or other key metrics together with your analytics data ?

  Getting started

  In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

  To summarize the things you have to do to get setup :

  • Install Piwik (for instance via git).
  • Activate the developer mode : ./console development:enable --full.
  • Generate a plugin : ./console generate:plugin --name="MyWidgetPlugin". There should now be a folder plugins/MyWidgetPlugin.
  • And activate the created plugin under Settings => Plugins.

  Let’s start creating a widget

  We start by using the Piwik Console to create a widget template :

  ./console generate:widget

  The command will ask you to enter the name of the plugin the widget should belong to. I will simply use the above chosen plugin name “MyWidgetPlugin”. It will ask you for a widget category as well. You can select any existing category, for instance “Visitors”, “Live !” or “Actions”, or you can define a new category, for instance your company name. There should now be a file plugins/MyWidgetPlugin/Widgets.php which contains already some examples to get you started easily :

  class Widgets extends \Piwik\Plugin\Widgets
  {
      /**
       * Here you can define the category the widget belongs to. You can reuse any existing widget category or define your own category.
       * @var string
       */
      protected $category = 'ExampleCompany';
   
      /**
       * Here you can add one or multiple widgets. You can add a widget by calling the method "addWidget()" and pass the name of the widget as well as a method name that should be called to render the widget. The method can be defined either directly here in this widget class or in the controller in case you want to reuse the same action for instance in the menu etc.
       */
      protected function init()
      {
          $this->addWidget('Example Widget Name', $method = 'myExampleWidget');
          $this->addWidget('Example Widget 2',    $method = 'myExampleWidget', $params = array('myparam' => 'myvalue'));
      }
   
      /**
       * This method renders a widget as defined in "init()". It's on you how to generate the content of the widget. As long as you return a string everything is fine. You can use for instance a "Piwik\View" to render a twig template. In such a case don't forget to create a twig template (eg. myViewTemplate.twig) in the "templates" directory of your plugin.
       *
       * @return string
       */
      public function myExampleWidget()
      {
          $view = new View('@MyWidgetPlugin/myViewTemplate');
          return $view->render();
      }
  }
  Télécharger

  As you might have noticed in the generated template we put emphasis on adding comments to explain you directly how to continue and where to get more information. Ideally this saves you some time and you don’t even have to search for more information on our developer pages. The category is defined in the property $category and can be changed at any time. Starting from Piwik 2.6.0 the generator will directly create a translation key if necessary to make it easy to translate the category into any language. Translations will be a topic in one of our future posts until then you can explore this feature on our Internationalization guide.

  A simple example

  We can define one or multiple widgets in the init method by calling addWidget($widgetName, $methodName). To do so we define the name of a widget which will be seen by your users as well as the name of the method that shall render the widget.

  protected $category = 'Example Company';
  
  
  
  public function init()
  
  {
  
      // Registers a widget named 'News' under the category 'Example Company'. 
  
      // The method 'myCorporateNews' will be used to render the widget.
  
      $this->addWidget('News', $method = 'myCorporateNews'); 
  
  }
  
  
  
  public function myCorporateNews()
  
  {
  
      return file_get_contents('http://example.com/news');
  
  }

  This example would display the content of the specified URL within the widget as defined in the method myCorporateNews. It’s on you how to generate the content of the widget. Any string returned by this method will be displayed within the widget. You can use for example a View to render a Twig template. For simplification we are fetching the content from another site. A more complex version would cache this content for faster performance. Caching and views will be covered in one of our future posts as well.

  

  Did you know ? To make your life as a developer as stress-free as possible the platform checks whether the registered method actually exists and whether the method is public. If not, Piwik will display a notification in the UI and advice you with the next step.

  Checking permissions

  Often you do not want to have the content of a widget visible to everyone. You can check for permissions by using one of our many convenient methods which all start with \Piwik\Piwik::checkUser*. Just to introduce some of them :

  // Make sure the current user has super user access
  
  \Piwik\Piwik::checkUserHasSuperUserAccess(); 
  
  
  
  // Make sure the current user is logged in and not anonymous
  
  \Piwik\Piwik::checkUserIsNotAnonymous(); 

  And here is an example how you can use it within your widget :

  public function myCorporateNews()
  
  {
  
      // Make sure there is an idSite URL parameter
  
      $idSite = Common::getRequestVar('idSite', null, 'int');
  
  
  
      // Make sure the user has at least view access for the specified site. This is useful if you want to display data that is related to the specified site.
  
      Piwik::checkUserHasViewAccess($idSite); 
  
  
  
      $siteUrl = \Piwik\Site::getMainUrlFor($idSite);
  
  
  
      return file_get_contents($siteUrl . '/news');
  
  }

  In case any condition is not met an exception will be thrown and an error message will be presented to the user explaining that he does not have enough permissions. You’ll find the documentation for those methods in the Piwik class reference.

  How to test a widget

  After you have created your widgets you are surely wondering how to test it. First, you should write a unit or integration test which we will cover in one of our future blog posts. Just one hint : You can use the command ./console generate:test to create a test. To manually test a widget you can add a widget to a dashboard or export it.

  Publishing your Plugin on the Marketplace

  In case you want to share your widgets with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin.

  Advanced features

  Isn’t it easy to create a widget ? We never even created a file ! Of course, based on our API design principle “The complexity of our API should never exceed the complexity of your use case.” you can accomplish more if you want : You can clarify parameters that will be passed to your widget, you can create a method in the Controller instead of the Widget class to make the same method also reusable for adding it to the menu, you can assign different categories to different widgets, you can remove any widgets that were added by the Piwik core or other plugins and more.

  Would you like to know more about widgets ? Go to our Widgets class reference in the Piwik Developer Zone.

  If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.

• JavaCV in Android : FFmpegFrameGrabber Class not found exception

  30 septembre 2014, par Sunshinetpu

  I want to create a video from images. So I tried to import JavaCV into Android project with the following guide :
  http://javacv4android.blogspot.com/2014/02/how-to-import-javacv-libraries-to.html
  But I have got error
  FFmpegFrameGrabber Class not found exception
  I don’t know how to fix the problem.
  Can any body help me ?
  Thanks a lot for advices.

• When using ffmpeg.exe to create video from sequence of images the result is avi file that show green color why ?

  9 janvier 2014, par user3163653

  In Form1 im taking screenshots of my screen I checked they are ok i save them to the hard disk and see they are ok.

  private void timer1_Tick(object sender, EventArgs e)
  
          {
  
  
  
              using (bitmap = (Bitmap)ScreenCapture.CaptureScreen(true))
  
              {
  
  
  
              Image mScreenImage = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
  
                                       Screen.PrimaryScreen.Bounds.Height);
  
              Graphics g = Graphics.FromImage(bitmap);
  
              g.CopyFromScreen(0, 0, 0, 0, new Size(bitmap.Width, bitmap.Height));
  
              g.Dispose();
  
                  bitmap.Save(@"D:\Testbmp\" + counter.ToString("D6") + ".jpg", ImageFormat.Jpeg);
  
                  counter++;
  
              ffmp.PushFrame((Bitmap)mScreenImage);
  
  
  
              }
  
  
  
          }

  Then in the new class ffmp im using pipe to get the screenshots and build the avi file in real time :

  using System;
  
  using System.Windows.Forms;
  
  using System.Collections.Generic;
  
  using System.Linq;
  
  using System.Text;
  
  using System.Threading.Tasks;
  
  using System.Drawing;
  
  using System.IO.Pipes;
  
  using System.Runtime.InteropServices;
  
  using System.Diagnostics;
  
  using System.IO;
  
  
  
  namespace ScreenVideoRecorder
  
  {
  
      class Ffmpeg
  
      {
  
          NamedPipeServerStream p;
  
          String pipename = "mytestpipe";
  
          System.Diagnostics.Process process;
  
          string ffmpegFileName = "ffmpeg.exe";
  
          string workingDirectory;
  
  
  
          public Ffmpeg()
  
          {
  
              workingDirectory = Path.GetDirectoryName(Application.ExecutablePath);
  
              Logger.Write("workingDirectory: " + workingDirectory);
  
              if (!Directory.Exists(workingDirectory))
  
              {
  
                  Directory.CreateDirectory(workingDirectory);
  
              }
  
              ffmpegFileName = Path.Combine(workingDirectory, ffmpegFileName);
  
              Logger.Write("FfmpegFilename: " + ffmpegFileName);
  
          }
  
  
  
          public void Start(string pathFileName, int BitmapRate)
  
          {
  
              try
  
              {
  
  
  
                  string outPath = pathFileName;
  
                  p = new NamedPipeServerStream(pipename, PipeDirection.Out, 1, PipeTransmissionMode.Byte);
  
  
  
                  ProcessStartInfo psi = new ProcessStartInfo();
  
                  psi.WindowStyle = ProcessWindowStyle.Hidden;
  
                  psi.UseShellExecute = false;
  
                  psi.CreateNoWindow = false;
  
                  psi.FileName = ffmpegFileName;
  
                  psi.WorkingDirectory = workingDirectory;
  
                  psi.Arguments = @"-f rawvideo -pix_fmt yuv420p -video_size 1920x1080 -i \\.\pipe\mytestpipe -map 0 -c:v mpeg4 -r " + BitmapRate + " " + outPath;
  
                  process = Process.Start(psi);
  
                  process.EnableRaisingEvents = false;
  
                  psi.RedirectStandardError = true;
  
                  p.WaitForConnection();
  
              }
  
              catch (Exception err)
  
              {
  
                  Logger.Write("Exception Error: " + err.ToString());
  
              }
  
          }
  
  
  
          public void PushFrame(Bitmap bmp)
  
          {
  
              try
  
              {
  
                  int length;
  
                  // Lock the bitmap's bits.
  
                  //bmp = new Bitmap(1920, 1080);
  
                  Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
  
                  //Rectangle rect = new Rectangle(0, 0, 1280, 720);
  
                  System.Drawing.Imaging.BitmapData bmpData =
  
                      bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly,
  
                      bmp.PixelFormat);
  
  
  
                  int absStride = Math.Abs(bmpData.Stride);
  
                  // Get the address of the first line.
  
                  IntPtr ptr = bmpData.Scan0;
  
  
  
                  // Declare an array to hold the bytes of the bitmap.
  
                  //length = 3 * bmp.Width * bmp.Height;
  
                  length = absStride * bmpData.Height;
  
                  byte[] rgbValues = new byte[length];
  
  
  
                  //Marshal.Copy(ptr, rgbValues, 0, length);
  
                  int j = bmp.Height - 1;
  
                  for (int i = 0; i < bmp.Height; i++)
  
                  {
  
                      IntPtr pointer = new IntPtr(bmpData.Scan0.ToInt32() + (bmpData.Stride * j));
  
                      System.Runtime.InteropServices.Marshal.Copy(pointer, rgbValues, absStride * (bmp.Height - i - 1), absStride);
  
                      j--;
  
                  }
  
                  p.Write(rgbValues, 0, length);
  
                  bmp.UnlockBits(bmpData);
  
              }
  
              catch(Exception err)
  
              {
  
                  Logger.Write("Error: " + err.ToString());
  
              }
  
  
  
          }
  
  
  
          public void Close()
  
          {
  
              p.Close();
  
          }
  
      }
  
  }

  This is the arguments im using now :

  psi.Arguments = @"-f rawvideo -pix_fmt yuv420p -video_size 1920x1080 -i \\.\pipe\mytestpipe -map 0 -c:v mpeg4 -r " + BitmapRate + " " + outPath;

  Before that I tried to use libx264 instead the mpeg4 but it didn't create the avi file good.
  The problem is that the avi file on the hard disk when I play it show just green color.
  I can play any other avi files on my hard disk but when playing this avi file I see green.

  

  And this is what I see when im playing the avi file :

  

  I tried to use Gspot to find if I need any codec to install and this is what I see :

  

  And I have ffdshow installed already so what should I do now ?