How to draw a polygon in OpenCV using Java?

A polygon with all the interior angles less than 180 is known as a convex polygon. The org.opencv.imgproc package of Java OpenCV library contains a class named Imgproc. To draw a polygon you need to invoke the fillConvexPoly() method of this class. This method accepts 3 parameters −

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

  • A MatOfPoint object points between which the polygon is to be drawn.

  • A Scalar object representing the color of the polygon.


import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfPoint;
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 DrawingConvexPolygon {
   public static void main(String args[]) {
      //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 an arrowed line
      MatOfPoint points = new MatOfPoint (
         new Point(108, 71), new Point(232, 52),
         new Point(321, 161), new Point(269, 250),
         new Point(126, 232), new Point(108, 71)
      Scalar color = new Scalar(64, 64, 64);
      Imgproc.fillConvexPoly (src, points, color);
      //Saving and displaying the image
      Imgcodecs.imwrite("arrowed_line.jpg", src);
      HighGui.imshow("Drawing an polygon", src);


On executing, the above program generates the following window −

Updated on: 10-Apr-2020


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