opencv12-计算物体旋转角度

求取的角度是负值，我在图中画了一个垂直的形状，得出的结果是0 ，原因大家自己去理解。

废话不多说，直接上代码：

#include <iostream>
#include <vector>
#include <opencv2/opencv.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace std;
using namespace cv;

int main()
{
// Read image
RNG rng(12345);
Mat pSrcImage = imread("11.jpg", CV_LOAD_IMAGE_UNCHANGED);
if (!pSrcImage.data)
return 0;
imshow("Image", pSrcImage);

// 转为2值图
threshold(pSrcImage, pSrcImage, 200, 255, cv::THRESH_BINARY_INV);

imwrite("binary.jpg", pSrcImage);

vector<std::vector<cv::Point>> contours;
Mat canny_output;
Canny(pSrcImage, canny_output, 80, 255, 3);
imshow("Canny Image",canny_output);

vector<Vec4i> hierarchy;
findContours(canny_output, contours, hierarchy, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));

/// 对每个找到的轮廓创建可倾斜的边界框和椭圆
vector<RotatedRect> minRect(contours.size());
for (unsigned int i = 0; i < contours.size(); i++)
{
minRect[i] = minAreaRect(Mat(contours[i]));
}

/// 绘出轮廓及其可倾斜的边界框
CvBox2D End_Rage2D;
CvPoint2D32f rectpoint[4];
Point2f rect_points[4];

Mat drawing = Mat::zeros(canny_output.size(), CV_8UC3);
for (unsigned int i = 0; i< contours.size(); i++)
{

End_Rage2D = minAreaRect(Mat(contours[i]));
Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
// contour
drawContours(drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point());
// rotated rectangle
Point2f rect_points[4]; minRect[i].points(rect_points);
for (unsigned int j = 0; j < 4; j++)
{
line(drawing, rect_points[j], rect_points[(j + 1) % 4], color, 1, 8);
cout << "坐标点："<<rect_points[j] << "........" << rect_points[(j + 1) % 4] << endl;
}

int a = 0, b = 0, k = 0;
a = (int)sqrt((pow((rect_points[0].x - rect_points[1].x), 2) + pow((rect_points[0].y - rect_points[1].y), 2)));
b = (int)sqrt((pow((rect_points[0].x - rect_points[3].x), 2) + pow((rect_points[0].y - rect_points[3].y), 2)));

if (a<b)
{
k = a;
a = b;
b = k;
}
printf("最小外接矩形的长为：%d，宽为：%d。\n\n", a, b);
cout << " angle:\n" << 90+(float)End_Rage2D.angle << std::endl; //旋转角度
}

namedWindow("Contours1", CV_WINDOW_AUTOSIZE);
imshow("Contours1", drawing);

waitKey(0);
return 0;

}实验图：



实验结果：