如何在倾斜文档中查找轮廓

Question

现在我正在使用

Imgproc.findContours(cannedImage, contours, hierarchy, Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);

找到轮廓，当文档直接放在相机前时工作正常。但它没有检测到倾斜的文件。知道如何在倾斜的文档中找到轮廓？

这是我的完整功能：

private ArrayList<MatOfPoint> findContours(Mat src) {

        double ratio = src.size().height / 500;
        int height = Double.valueOf(src.size().height / ratio).intValue();
        int width = Double.valueOf(src.size().width / ratio).intValue();
        Size size = new Size(width, height);

        Mat resizedImage = new Mat(size, CvType.CV_8UC4);
        Mat grayImage = new Mat(size, CvType.CV_8UC4);
        Mat cannedImage = new Mat(size, CvType.CV_8UC1);

        Imgproc.resize(src, resizedImage, size);
        Imgproc.cvtColor(resizedImage, grayImage, Imgproc.COLOR_RGBA2GRAY, 4);
        Imgproc.GaussianBlur(grayImage, grayImage, new Size(5, 5), 0);
        Imgproc.Canny(grayImage, cannedImage, 75, 200);

        ArrayList<MatOfPoint> contours = new ArrayList<>();
        Mat hierarchy = new Mat();

        Imgproc.findContours(cannedImage, contours, hierarchy, Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);

        hierarchy.release();

        Collections.sort(contours, new Comparator<MatOfPoint>() {

            @Override
            public int compare(MatOfPoint lhs, MatOfPoint rhs) {
                return Double.valueOf(Imgproc.contourArea(rhs)).compareTo(Imgproc.contourArea(lhs));
            }
        });

        resizedImage.release();
        grayImage.release();
        cannedImage.release();

        return contours;
    }