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Yes i already use approxPolyDP() in my code

  private boolean isRectangle(MatOfPoint2f polygon, int srcArea) {
    MatOfPoint polygonInt = GeomUtils.toMatOfPointInt(polygon);

    if (polygon.rows() != 4) {
        return false;
    }

    double area = Math.abs(Imgproc.contourArea(polygon));
    if (area < srcArea * areaLowerThresholdRatio || area > srcArea * areaUpperThresholdRatio) {
        return false;
    }

    if (!Imgproc.isContourConvex(polygonInt)) {
        return false;
    }

    // Check if the all angles are more than 72.54 degrees (cos 0.3).
    double maxCosine = 0;
    Point[] approxPoints = polygon.toArray();

    for (int i = 2; i < 5; i++) {
        double cosine = Math.abs(GeomUtils.angle(approxPoints[i % 4], approxPoints[i - 2], approxPoints[i - 1]));
        maxCosine = Math.max(cosine, maxCosine);
    }

    if (maxCosine >= 0.3) {
        return false;
    }
    return true;
}

Do you have any other working code then please tell me

Thanks

Yes @missing i already use approxPolyDP() in my code

  private boolean isRectangle(MatOfPoint2f polygon, int srcArea) {
    MatOfPoint polygonInt = GeomUtils.toMatOfPointInt(polygon);

    if (polygon.rows() != 4) {
        return false;
    }

    double area = Math.abs(Imgproc.contourArea(polygon));
    if (area < srcArea * areaLowerThresholdRatio || area > srcArea * areaUpperThresholdRatio) {
        return false;
    }

    if (!Imgproc.isContourConvex(polygonInt)) {
        return false;
    }

    // Check if the all angles are more than 72.54 degrees (cos 0.3).
    double maxCosine = 0;
    Point[] approxPoints = polygon.toArray();

    for (int i = 2; i < 5; i++) {
        double cosine = Math.abs(GeomUtils.angle(approxPoints[i % 4], approxPoints[i - 2], approxPoints[i - 1]));
        maxCosine = Math.max(cosine, maxCosine);
    }

    if (maxCosine >= 0.3) {
        return false;
    }
    return true;
}

Do you have any other working code then please tell me

Thanks

Yes @missing i already use approxPolyDP() in my code

  Imgproc.findContours(gray, contours, new Mat(), Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);
        int i=0;
        for (MatOfPoint contour : contours) {
            MatOfPoint2f contourFloat = GeomUtils.toMatOfPointFloat(contour);
            double arcLen = Imgproc.arcLength(contourFloat, true) * 0.02;

            // Approximate polygonal curves.
            MatOfPoint2f approx = new MatOfPoint2f();
            Imgproc.approxPolyDP(contourFloat, approx, arcLen, true);

            if (isRectangle(approx, srcArea)) {
                Imgproc.drawContours(src, contours, i, new Scalar(255, 0, 0), 3);
            }
        }

  private boolean isRectangle(MatOfPoint2f polygon, int srcArea) {
    MatOfPoint polygonInt = GeomUtils.toMatOfPointInt(polygon);

    if (polygon.rows() != 4) {
        return false;
    }

    double area = Math.abs(Imgproc.contourArea(polygon));
    if (area < srcArea * areaLowerThresholdRatio || area > srcArea * areaUpperThresholdRatio) {
        return false;
    }

    if (!Imgproc.isContourConvex(polygonInt)) {
        return false;
    }

    // Check if the all angles are more than 72.54 degrees (cos 0.3).
    double maxCosine = 0;
    Point[] approxPoints = polygon.toArray();

    for (int i = 2; i < 5; i++) {
        double cosine = Math.abs(GeomUtils.angle(approxPoints[i % 4], approxPoints[i - 2], approxPoints[i - 1]));
        maxCosine = Math.max(cosine, maxCosine);
    }

    if (maxCosine >= 0.3) {
        return false;
    }
    return true;
}

Do you have any other working code then please tell me

Thanks