Android OpenCV FindRectangle算法无法正常工作

Question

我正在尝试使用此代码http://androiderstuffs.blogspot.com/2016/06/detecting-rectangle-using-opencv-java.html来检测卡片。但是我不会把卡片放在平面上，而是将手中的卡片放在我的头前。问题是，它没有检测卡矩形。我是OpenCV的新手。请参阅下面的代码，此代码将突出显示输出图像中找到的所有矩形。问题是，它永远找不到卡片矩形。

    private void findRectangleOpen(Bitmap image) throws Exception {
    Mat tempor = new Mat();
    Mat src = new Mat();
    Utils.bitmapToMat(image, tempor);

    Imgproc.cvtColor(tempor, src, Imgproc.COLOR_BGR2RGB);

    Mat blurred = src.clone();
    Imgproc.medianBlur(src, blurred, 9);

    Mat gray0 = new Mat(blurred.size(), CvType.CV_8U), gray = new Mat();

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

    List<Mat> blurredChannel = new ArrayList<Mat>();
    blurredChannel.add(blurred);
    List<Mat> gray0Channel = new ArrayList<Mat>();
    gray0Channel.add(gray0);

    MatOfPoint2f approxCurve;


    int maxId = -1;

    for (int c = 0; c < 3; c++) {
        int ch[] = {c, 0};
        Core.mixChannels(blurredChannel, gray0Channel, new MatOfInt(ch));

        int thresholdLevel = 1;
        for (int t = 0; t < thresholdLevel; t++) {
            if (t == 0) {
                Imgproc.Canny(gray0, gray, 10, 20, 3, true); // true ?
                Imgproc.dilate(gray, gray, new Mat(), new Point(-1, -1), 1); // 1
                // ?
            } else {
                Imgproc.adaptiveThreshold(gray0, gray, thresholdLevel,
                        Imgproc.ADAPTIVE_THRESH_GAUSSIAN_C,
                        Imgproc.THRESH_BINARY,
                        (src.width() + src.height()) / 200, t);
            }

            Imgproc.findContours(gray, contours, new Mat(),
                    Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);
            int i = 0;
            for (MatOfPoint contour : contours) {
                MatOfPoint2f temp = new MatOfPoint2f(contour.toArray());
                double area = Imgproc.contourArea(contour);
                approxCurve = new MatOfPoint2f();
                Imgproc.approxPolyDP(temp, approxCurve,
                        Imgproc.arcLength(temp, true) * 0.02, true);

                if (approxCurve.total() == 4 && area >= 200 && area <= 40000) {

                    double maxCosine = 0;

                    List<Point> curves = approxCurve.toList();
                    for (int j = 2; j < 5; j++) {

                        double cosine = Math.abs(angle(curves.get(j % 4),
                                curves.get(j - 2), curves.get(j - 1)));
                        maxCosine = Math.max(maxCosine, cosine);
                    }

                    if (maxCosine < 0.3) {
                        Imgproc.drawContours(src, contours, i, new Scalar(255, 0, 0), 3);
                        Bitmap bmp;
                        bmp = Bitmap.createBitmap(src.cols(), src.rows(),
                                Bitmap.Config.ARGB_8888);
                        Utils.matToBitmap(src, bmp);

                        ByteArrayOutputStream stream = new ByteArrayOutputStream();
                        bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
                        byte[] byteArray = stream.toByteArray();
                        //File origFile = getFileForSaving();
                        savePhoto(byteArray);
                        bmp.recycle();
                    }
                }
                i++;
            }
        }
    }

}
private static double angle(org.opencv.core.Point p1, org.opencv.core.Point p2, org.opencv.core.Point p0) {
    double dx1 = p1.x - p0.x;
    double dy1 = p1.y - p0.y;
    double dx2 = p2.x - p0.x;
    double dy2 = p2.y - p0.y;
    return (dx1 * dx2 + dy1 * dy2)
            / sqrt((dx1 * dx1 + dy1 * dy1) * (dx2 * dx2 + dy2 * dy2)
            + 1e-10);
}

示例输出图像是： Output of detecting rectangle