Finding area of convex hull in java

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Java

OpenCV

Hi,I'm very new to image processing.I'm trying to calculate the solidity in opencv on contours of an image. But contourArea() method in my code gives an assertion error that is:

"OpenCV Error: Assertion failed
(contour.checkVector(2) >= 0 &&
(contour.depth() == CV_32F || contour.depth() == CV_32S))
in cv::contourArea").


How can I fix it. Thank You.

What I have tried:

import static com.googlecode.javacv.cpp.opencv_imgproc.CV_THRESH_BINARY;
import java.util.ArrayList;
import java.util.List;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfInt;
import org.opencv.core.MatOfPoint;
import org.opencv.core.Scalar;
import org.opencv.highgui.Highgui;
import org.opencv.imgproc.Imgproc;
import static org.opencv.imgproc.Imgproc.contourArea;
import static org.opencv.imgproc.Imgproc.findContours;


public class Solidity {
    public static void main(String[] args) {
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        Mat image = Highgui.imread("D:\\MyImage.bmp");

        if (image.empty() == true) {
            System.out.println("Error: no image found!");
        } else {

            List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
            Mat image_2 = new Mat();


            Imgproc.cvtColor(image, image_2, Imgproc.COLOR_BGR2GRAY);
            Imgproc.threshold(image_2, image_2, 150, 255, CV_THRESH_BINARY);

            findContours(image_2, contours, new Mat(), Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);           


            for (int i = 0; i < contours.size(); i++) {
                Imgproc.drawContours(image, contours, -1, new Scalar(240, 0, 0), 2);

                double area=contourArea(contours.get(i));

                MatOfInt matOfInt=new MatOfInt();

                Imgproc.convexHull(contours.get(i),matOfInt);

                //Mat conMat=new Mat(contours.get(i).size(),CV_32FC1);
                //Error comes from here
                double hullArea=contourArea(matOfInt);

                double solidity=area/hullArea;

                System.out.println(solidity);
            }

        }

    }
}