How to draw polylines in OpenCV using Java?

The org.opencv.imgproc package of Java OpenCV library contains a class named Imgproc this class provides various methods to process an input image such as resize(), filter2D, etc.. In addition to these It also provides a set of method to draw geometrical shapes on images.

Among them to draw a polylines you need to invoke the polylines() method of this class. This method accepts the following parameters −

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

• A-List object holding the objects of the type MatOfPoint.

• A parameter of the type boolean specifying whether the poly-lines are closed.

• A Scalar object representing the color of the polygon.

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

Example

import java.util.ArrayList; import java.util.List; 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 DrawingPolyines {    Mat matrix = null;    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 an polygon       List<MatOfPoint> list = new ArrayList<MatOfPoint>();       list.add( new MatOfPoint (          new Point(208, 71), new Point(421, 161),          new Point(226, 232), new Point(332, 52),          new Point(363, 250)));       boolean isClosed = true;       Scalar color = new Scalar(64, 64, 64);       int thickness = 10;       Imgproc.polylines (src, list, isClosed, color, thickness);       //Saving and displaying the image       Imgcodecs.imwrite("arrowed_line.jpg", src);       HighGui.imshow("Drawing a polylines", src);       HighGui.waitKey();    } }

Output

On executing, the above program generates the following window −