How to draw a rectangle in OpenCV using Java?

The org.opencv.imgproc package of Java OpenCV library contains a class named Imgproc. To draw a rectangle you need to invoke the rectangle() method of this class. This method accepts the following parameters −

  • A Mat object representing the image on which the rectangle is to be drawn.

  • Two Point objects representing the vertices of the rectangle that is to be drawn.

  • A Scalar object representing the color of the rectangle(BGR).

  • An integer representing the thickness of the rectangle(default:1).


import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.Point;
import org.opencv.core.Scalar;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
public class DrawingRectangle {
   public static void main(String args[]) {
      // Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      //Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      //Reading the source image in to a Mat object
      Mat src = Imgcodecs.imread("D:\images\blank.jpg");
      //Drawing a Rectangle
      Point point1 = new Point(100, 100);
      Point point2 = new Point(500, 300);
      Scalar color = new Scalar(64, 64, 64);
      int thickness = 10;
      Imgproc.rectangle (src, point1, point2, color, thickness);
      //Saving and displaying the image
      Imgcodecs.imwrite("arrowed_line.jpg", src);
      HighGui.imshow("Drawing a rectangle", src);


On executing, the above program generates the following window −

Updated on: 09-Apr-2020


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