opencv（Python/c++）:画矩形框（普通的与旋转的矩形框）

青旅半醒 2022-03-08 09:36 925阅读 0赞

后续参考：  
利用OpenCV提取图像中的矩形区域（PPT屏幕等）：后续凸包什么的可以参考这个。  
[https://segmentfault.com/a/1190000013925648][https_segmentfault.com_a_1190000013925648]

我们常常需要用矩形框

### 效果图1：普通矩形+文字 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc1NTM4NA_size_16_color_FFFFFF_t_70]

#include<opencv2/core/core.hpp>
    #include<opencv2/highgui/highgui.hpp>
    #include "opencv2/imgproc/imgproc.hpp"
    using namespace cv;
    
    //宏定义部分
    
    #define Win_Name3 "矩阵+字"
    //main函数
    int main(int argc,char** argv)
    { 
    
    Mat image3 = Mat::zeros(800, 800, CV_8UC3);//生成一个800x800的窗口
    rectangle (image3, Point(100, 300), Point(700, 500), Scalar(0, 0, 255), 2, 8, 0);//黄色矩形框
    
    putText(image3,"hit area",Point(100, 300),FONT_HERSHEY_SIMPLEX,1,Scalar(255,0,0),2);
    imshow(Win_Name3, image3);
    while(1)
    { 
        int key=cvWaitKey(10);
    if (key==27)
    { 
        break;
    }
    }
    
    
    return 0;
    
    }

### 效果图2：旋转矩形 ###

目前opencv中没有直接绘制旋转矩形的函数，而是通过自主绘制的。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc1NTM4NA_size_16_color_FFFFFF_t_70 1]

#include <opencv2/opencv.hpp>
    #include <iostream>
    
    using namespace std;
    using namespace cv;
    
    int main()
    { 
        Mat image_source = imread("/home/liuxin/桌面/opencv/hammer.jpeg");
        vector<Point> vec_pts;
        Point p1(800,400), p2(1100,605), p3(902,970), p4(802,780);//随意给了4个点
        vec_pts.push_back(p1);
        vec_pts.push_back(p2);
        vec_pts.push_back(p3);
        vec_pts.push_back(p4);
        //将四个点表示出来，以圆的形式
        circle(image_source,p1,20,Scalar(0,255,255),5);
        circle(image_source,p2,20,Scalar(0,255,255),5);
        circle(image_source,p3,20,Scalar(0,255,255),5);
        circle(image_source,p4,20,Scalar(0,255,255),5);
    
    
        //根据外接矩形的顶点，再一个一个连线连起来，构成带角度的矩形
        RotatedRect rect = minAreaRect(vec_pts);//外接矩形
        Point2f vertices[4];
        rect.points(vertices);//外接矩形的4个顶点
        for (int i = 0; i < 4; i++)//画矩形
            line(image_source , vertices[i], vertices[(i + 1) % 4], Scalar(255, 0, 0),3);
    
        imshow("rotation rect", image_source);
    
    
    
        //将roi区域提取出来
        Point2f center = rect.center;//外接矩形中心点坐标
        Mat rot_mat = getRotationMatrix2D(center, rect.angle, 1.0);//求旋转矩阵
        Mat rot_image;
        Size dst_sz(image_source.size());
        warpAffine(image_source, rot_image, rot_mat, dst_sz);//原图像旋转
        Mat result1 = rot_image(Rect(center.x - (rect.size.width / 2),
                                     center.y - (rect.size.height/2),
                                     rect.size.width,
                                     rect.size.height));//提取ROI
        imshow("result", result1);
    
        while(1)
        { 
            int key=cvWaitKey(10);
        if (key==27)
        { 
            break;
        }
        }
    
    
        return 0;
    
        return 0;
    }

[https_segmentfault.com_a_1190000013925648]: https://segmentfault.com/a/1190000013925648
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc1NTM4NA_size_16_color_FFFFFF_t_70]: /images/20220308/a391053da414476d9072a01097a60d7a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjc1NTM4NA_size_16_color_FFFFFF_t_70 1]: /images/20220308/03f315b71efd4cc4882c55141b2d7aa0.png