Droidcv - Libraries built on top of Opencv4Android

• Route the display of an Android device to OpenCv and do all the image processing operations as you would do with a normal Mat object.

  Requirements :

  • Rooted device.
  • The app must be pushed into /system/priv-app
  • The device must have Kitkat

  Demo : https://www.youtube.com/watch?v=xKVsemXU8yk&feature=youtu.be

  Usage :

  Since while processing the display of your Android you will want your app to be run on the background, so we will be writing the core code inside a service. You will need to extend the abstract service class CoreDisplayService.

  public class SampleService extends CoreDisplayService {
  
    /**
     * This method must be implemented and the resource identifier to the classifier file
     * shoud be returned.
     */
    @Override
    public int setClassifier() {        
        return R.raw.lbpcascade_frontalface;
    }
  
    /**
     * Override this method to receive a new frame.
     * Call frame.gray() or frame.rgba() to get the respective Mat objects.
     * Note : I'm not able to generate rgba image, so for now frame.rgba() will
     * also return the grayscale Mat.
     */
    @Override
    public void onNewFrame(CameraBridgeViewBase.CvCameraViewFrame frame) {
        //Call the super method only for debugging purposes
        super.onNewFrame(frame);
        Mat gray = frame.gray();
        //TODO: Do what you want with the Mat object
    }
  
    /**
     * Override this method to receive the raw frame in the form of bytes.
     * Note : The format of this frame will be according to the output format of the decoder.
     */
    @Override
    public void rawFrame(final byte[] frame) {
        //TODO: Callback for getting the raw frames       
    }
  
    @Override
    public void onDisplayFrameStarted() {
        //TODO: Callback when the codec is just going to start
    }
  
    @Override
    public void onDisplayFrameStopped() {
        //TODO: Callback when the codec finishes
    }
  
    @Override
    public void decoderOutputFormatChanged(MediaFormat format) {
        //TODO: Override this to get info about the output format of the decoder
    }
  }
  

  You can start this service the normal way :

  startService(new Intent(mContext, SampleService.class));
  

  And don't forget to add the service to the AndroidManifest.xml file.

  Behind the scene :

  I create a virtual Surface and route the output of Android's display to the surface using DisplayMAnager API. Then I use this Surface as an input to the video encoder. Then I pass the ouput of the encoder to a video decoder. And the output from the video decoder is in the form of raw frames on which I do the further processing.