content: import org.opencv.core.Core;
  import org.opencv.core.CvType;
  import org.opencv.core.Mat;
  import org.opencv.highgui.HighGui;
  import org.opencv.imgcodecs.Imgcodecs;
  import org.opencv.imgproc.Imgproc;
  
  class Remap {
      private Mat mapX = new Mat();
      private Mat mapY = new Mat();
      private Mat dst = new Mat();
      private int ind = 0;
  
      //! [Update]
      private void updateMap() {
          float buffX[] = new float[(int) (mapX.total() * mapX.channels())];
          mapX.get(0, 0, buffX);
  
          float buffY[] = new float[(int) (mapY.total() * mapY.channels())];
          mapY.get(0, 0, buffY);
  
          for (int i = 0; i < mapX.rows(); i++) {
              for (int j = 0; j < mapX.cols(); j++) {
                  switch (ind) {
                  case 0:
                      if( j > mapX.cols()*0.25 && j < mapX.cols()*0.75 && i > mapX.rows()*0.25 && i < mapX.rows()*0.75 ) {
                          buffX[i*mapX.cols() + j] = 2*( j - mapX.cols()*0.25f ) + 0.5f;
                          buffY[i*mapY.cols() + j] = 2*( i - mapX.rows()*0.25f ) + 0.5f;
                      } else {
                          buffX[i*mapX.cols() + j] = 0;
                          buffY[i*mapY.cols() + j] = 0;
                      }
                      break;
                  case 1:
                      buffX[i*mapX.cols() + j] = j;
                      buffY[i*mapY.cols() + j] = mapY.rows() - i;
                      break;
                  case 2:
                      buffX[i*mapX.cols() + j] = mapY.cols() - j;
                      buffY[i*mapY.cols() + j] = i;
                      break;
                  case 3:
                      buffX[i*mapX.cols() + j] = mapY.cols() - j;
                      buffY[i*mapY.cols() + j] = mapY.rows() - i;
                      break;
                  default:
                      break;
                  }
              }
          }
          mapX.put(0, 0, buffX);
          mapY.put(0, 0, buffY);
          ind = (ind+1) % 4;
      }
      //! [Update]
  
      public void run(String[] args) {
          String filename = args.length > 0 ? args[0] : "../data/chicky_512.png";
          //! [Load]
          Mat src = Imgcodecs.imread(filename, Imgcodecs.IMREAD_COLOR);
          if (src.empty()) {
              System.err.println("Cannot read image: " + filename);
              System.exit(0);
          }
          //! [Load]
  
          //! [Create]
          mapX = new Mat(src.size(), CvType.CV_32F);
          mapY = new Mat(src.size(), CvType.CV_32F);
          //! [Create]
  
          //! [Window]
          final String winname = "Remap demo";
          HighGui.namedWindow(winname, HighGui.WINDOW_AUTOSIZE);
          //! [Window]
  
          //! [Loop]
          for (;;) {
              updateMap();
              Imgproc.remap(src, dst, mapX, mapY, Imgproc.INTER_LINEAR);
              HighGui.imshow(winname, dst);
              if (HighGui.waitKey(1000) == 27) {
                  break;
              }
          }
          //! [Loop]
          System.exit(0);
      }
  }
  
  public class RemapDemo {
      public static void main(String[] args) {
          // Load the native OpenCV library
          System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
  
          new Remap().run(args);
      }
  }
  