Documentation

Plugins API

Technically a plugin is a class, either written in C++, Java or ObjC, that is derived from the wikitude Plugin base class. Beside lifecycle handling and options to enable and disable the plugin, the Plugin class has two main methods that you can override

cameraFrameAvailable, which is called each time the camera has a new frame update, which is called each time the wikitude SDK renders a new frame

Plugin Base Class

class Plugin {
   public:
      Plugin();
      ~Plugin();
      string identifier() const; // returns a unique plugin identifier
      bool processesColorCameraFrames(); // returns true if the plugins wants to process color frames instead of bw

      void setEnabled(bool enabled_);
      bool isEnabled();

      string callJavaScript(string javaScriptSnippet); // evaluates the given JavaScript snippet in the currently loaded ARchitect World context.

   protected:
      void initialize(); // called when the plugin is initially added to the Wikitude SDK
      void pause(); // called when the Wikitude SDK is paused e.g. the application state changes from active to background
      void resume(uint pausedTime_); // called when the Wikitude SDK resumes e.g. from background to active state. pausedTime represents the time in milliseconds that the plugin was not updated.
      void destroy(); // called when the plugin is removed from the Wikitude SDK

      void cameraFrameAvailable(const Frame&; cameraFrame_); // called each time the camera has a new frame
      void update(const vector<RecognizedTarget> recognizedTargets_); // called each time the Wikitude SDK renders a new frame

   protected:
      string      _identifier;
      bool        _enabled;
};

With those methods in place your plugin will be able to read the full camera image for your own purpose, where the YUV image is also processed in wikitude’s computer vision engine.

Information about Recognized Targets

In case you have the wikitude SDK running with ongoing image recognition, the plugin API will populate the RecognizedTarget in the update method once an image has been recognized. The plugin can then work with class RecognizedTarget, which wraps the details of the target image in the camera view. With that you can read out the pose of the target image and use it for your purposes. Additionally the call contains the calculated distance to the recognized target

class RecognizedTarget {
   public:
      const string&    getIdentifier() const; // the identifier of the target. The identifier is defined when the target is added to a target collection
      const Mat4&      getModelViewMatrix() const; // the model view matrix that defines the transformation of the target in the camera frame (translation, rotation, scale)
      const Mat4&      getProjectionMatrix() const;
      const float      getDistanceToCamera() const; // represents the distance from the target to the camera in millimeter
};

Passing values from within the plugin to the JavaScript part of your augmented reality experience is done via the `addToJavaScriptQueue()`` method of the Plugin class. Using this function will execute any JavaScript code in the context of your augmented reality experience.

Barcode and QR code reader

This samples shows a full implementation of the popular barcode library ZBar into the Wikitude SDK. As ZBar is licensed under LGPL2.1 this sample can also be used for other projects.

ZBar is an open source software suite for reading bar codes from various sources, such as video streams, image files and raw intensity sensors. It supports many popular symbologies (types of bar codes) including EAN-13/UPC-A, UPC-E, EAN-8, Code 128, Code 39, Interleaved 2 of 5 and QR Code.