java opencv 获取图中物品的倾斜角度（单个物品，如果存在多个物品，建议先将多个物品处理成一个整体或分别切割开处理）

// 1、先连上opencv包

System.setProperty("java.awt.headless", "false");
System.out.println(System.getProperty("java.library.path"));
URL url = ClassLoader.getSystemResource("lib/opencv/opencv_java4100.dll");
System.load(url.getPath());

// 2、计算倾斜的角度

String filePath = "需要处理的文件路径";
Mat src = Imgcodecs.imread(filePath);
Mat gary = new Mat();
Imgproc.cvtColor(src, gary, Imgproc.COLOR_RGB2GRAY);
Imgproc.GaussianBlur(gary, gary, new Size(3, 3), 0);
Imgproc.GaussianBlur(gary, gary, new Size(3, 3), 0);
Mat edge = new Mat();
Imgproc.Canny(gary, edge, 30, 50);

Mat lines = new Mat();
Imgproc.HoughLinesP(edge, lines, 1, Math.PI/180, 100, 50, 10);

double angle = 0.0;
for (int i = 0; i < lines.cols(); i++) {
    double rho = lines.get(0, i)[0];
    double theta = lines.get(0, i)[1];
    double cosTheta = Math.cos(theta);
    double sinTheta = Math.sin(theta);
    double x0 = rho * cosTheta;
    double y0 = rho * sinTheta;
    double x1 = x0 + 1000 * (-sinTheta);
    double y1 = y0 + 1000 * (cosTheta);
    double x2 = x0 - 1000 * (-sinTheta);
    double y2 = y0 - 1000 * (cosTheta);

    angle += Math.atan2(y2 - y1, x2 - x1) * 180.0 / Math.PI;
}
angle /= lines.cols();
System.out.println("angle = " + angle);

if (angle < 0){
    angle = 180 - angle;
}

// 3、旋转图像并显示，其实opencv也可以旋转图像，但效果感觉不如Java

BufferedImage image = ImageIO.read(new File(filePath));

BufferedImage rotate = ImageUtils.Rotate(image, angle);

BufferedImage grayImage = new BufferedImage(rotate.getWidth(),rotate.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
ColorConvertOp op = new ColorConvertOp(null);
grayImage = op.filter(rotate, grayImage);

Mat src = Mat.zeros(new Size(rotate.getWidth(), rotate.getHeight()), CvType.CV_8UC3);

byte[] imageData = ((DataBufferByte) grayImage.getRaster().getDataBuffer()).getData();
src.put(0,0,imageData);

HighGui.namedWindow("dst", HighGui.WINDOW_NORMAL);
HighGui.resizeWindow("dst", 1600, 900);
HighGui.imshow("dst", dst);
HighGui.waitKey(0);

src.release();
gary.release();
edge.release();
lines.release();

HighGui.destroyAllWindows();
System.exit(0);









// 上面 ImageUtils.Rotate是一个自定义的旋转方法，具体代码如下：

    //region 图片旋转
    /**

     * 对图片进行旋转

     *

     * @param src 被旋转图片

     * @param angel 旋转角度

     * @return 旋转后的图片

     */

    public static BufferedImage Rotate(Image src, int angel) {

        int src_width = src.getWidth(null);

        int src_height = src.getHeight(null);

// 计算旋转后图片的尺寸

        Rectangle rect_des = CalcRotatedSize(new Rectangle(new Dimension(

                src_width, src_height)), angel);

        BufferedImage res = null;

        res = new BufferedImage(rect_des.width, rect_des.height,

                BufferedImage.TYPE_INT_RGB);

        Graphics2D g2 = res.createGraphics();

// 进行转换

        g2.translate((rect_des.width - src_width) / 2,

                (rect_des.height - src_height) / 2);

        g2.rotate(Math.toRadians(angel), src_width / 2, src_height / 2);

        g2.drawImage(src, null, null);

        return res;

    }

    /**

     * 计算旋转后的图片

     *

     * @param src 被旋转的图片

     * @param angel 旋转角度

     * @return 旋转后的图片

     */

    public static Rectangle CalcRotatedSize(Rectangle src, int angel) {

// 如果旋转的角度大于90度做相应的转换

        if (angel >= 90) {

            if (angel / 90 % 2 == 1) {

                int temp = src.height;

                src.height = src.width;

                src.width = temp;

            }

            angel = angel % 90;

        }

        double r = Math.sqrt(src.height * src.height + src.width * src.width) / 2;

        double len = 2 * Math.sin(Math.toRadians(angel) / 2) * r;

        double angel_alpha = (Math.PI - Math.toRadians(angel)) / 2;

        double angel_dalta_width = Math.atan((double) src.height / src.width);

        double angel_dalta_height = Math.atan((double) src.width / src.height);

        int len_dalta_width = (int) (len * Math.cos(Math.PI - angel_alpha

                - angel_dalta_width));

        int len_dalta_height = (int) (len * Math.cos(Math.PI - angel_alpha

                - angel_dalta_height));

        int des_width = src.width + len_dalta_width * 2;

        int des_height = src.height + len_dalta_height * 2;

        return new Rectangle(new Dimension(des_width, des_height));

    }

    //endregion