一、OpenCV知识点

1.OpenCV裁剪矩形区域赋值


  
   
    
     
    
    
     
      Mat img;
      //读取图像
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     
      cv::Rect rect(x, y, WIDTH, HEIGHT);
      //定义坐标（x,y）为矩形的左上角起点，宽高为WIDTH和HEIGHT的矩形
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     
      Mat tmp = 
      img(rect);
      //将img上矩形框住的部分赋给tmp

2.OpenCV将Mat粘贴到指定位置


  
   
    
     
    
    
     
      cv::Mat src;
      //读取图像
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     
      cv::Mat image;
      //定义一个存放图像的Mat
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     
      cv::Rect rect(0, 0, src.cols, src.rows);
      //定义坐标(0,0)为矩形的左上角起点，宽高为src.cols, src.rows的矩形
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     
      src.
      copyTo(
      image(rect));
      //把src的内容复制到image指定的Rect框中

二、程序样例

1.程序源码

代码如下（带注释）：


  
   
    
     
    
    
     
      #include <iostream>
     
    
   
    
     
    
    
     
      #include <opencv.hpp>
     
    
   
    
     
    
    
     
      using 
      namespace std;
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     
      int main()
     
    
   
    
     
    
    
     
      {
     
    
   
    
     
    
    
         
      //读视频
     
    
   
    
     
    
    
     	
      cv::VideoCapture videoLeftUp("kll.mp4");
     
    
   
    
     
    
    
     	
      cv::VideoCapture videoRightUp("kll.mp4");
     
    
   
    
     
    
    
     	
      cv::VideoCapture videoLeftDown("kll.mp4");
     
    
   
    
     
    
    
     	
      cv::VideoCapture videoRightDown("kll.mp4");
     
    
   
    
     
    
    
     	
      int fps = videoLeftUp.
      get(
      5);
     
    
   
    
     
    
    
     
      	cv::Size size = cv::
      Size(videoLeftUp.
      get(
      3), videoLeftUp.
      get(
      4));
     
    
   
    
     
    
    
     	
      //写视频
     
    
   
    
     
    
    
         
      cv::VideoWriter writer("kllHeBing.mp4", CV_FOURCC('m', 'p', '4', 'v'), fps, size, true);
     
    
   
    
     
    
    
     
      	cv::Mat frameLeftUp, frameRightUp, frameLeftDown, frameRightDown;
     
    
   
    
     
    
    
     	
      //读视频帧
     
    
   
    
     
    
    
         
      while (videoLeftUp.
      read(frameLeftUp) && videoRightUp.
      read(frameRightUp) &&
     
    
   
    
     
    
    
     
      		videoLeftDown.
      read(frameLeftDown) && videoRightDown.
      read(frameRightDown))
     
    
   
    
     
    
    
     
      	{
     
    
   
    
     
    
    
             
      //调整帧尺寸
     
    
   
    
     
    
    
     
      		cv::Mat frameLeftUpNew, frameRightUpNew, frameLeftDownNew, frameRightDownNew;
     
    
   
    
     
    
    
     		
      resize(frameLeftUp, frameLeftUpNew, cv::
      Size(frameLeftUp.cols / 
      2, frameLeftUp.rows / 
      2));
     
    
   
    
     
    
    
     		
      resize(frameRightUp, frameRightUpNew, cv::
      Size(frameRightUp.cols / 
      2, frameRightUp.rows / 
      2));
     
    
   
    
     
    
    
     		
      resize(frameLeftDown, frameLeftDownNew, cv::
      Size(frameLeftDown.cols / 
      2, frameLeftDown.rows / 
      2));
     
    
   
    
     
    
    
     		
      resize(frameRightDown, frameRightDownNew, cv::
      Size(frameRightDown.cols / 
      2, frameRightDown.rows / 
      2));
     
    
   
    
     
    
    
     		
      //新建Mat 用于图像合并
     
    
   
    
     
    
    
     
      		cv::Mat frameOut = cv::Mat::
      zeros(frameLeftUp.rows, frameLeftUp.cols, frameLeftUp.
      type());
     
    
   
    
     
    
    
             
      //定义图像放的位置
     
    
   
    
     
    
    
     
      		cv::Rect rectLeftUp = 
      cvRect(
      0, 
      0, frameLeftUpNew.cols, frameLeftUpNew.rows);
     
    
   
    
     
    
    
     
      		cv::Rect rectRightUp = 
      cvRect(frameRightUpNew.cols, 
      0, frameRightUpNew.cols, frameRightUpNew.rows);
     
    
   
    
     
    
    
     
      		cv::Rect rectLeftDown = 
      cvRect(
      0, frameLeftDownNew.rows, frameLeftDownNew.cols, frameLeftDown.rows);
     
    
   
    
     
    
    
     
      		cv::Rect rectRightDown = 
      cvRect(frameRightDownNew.cols, frameRightDownNew.rows, frameRightDownNew.cols, frameRightDownNew.rows);
     
    
   
    
     
    
    
     		
      //将调整尺寸的帧图像放置新建Mat的指定位置
     
    
   
    
     
    
    
     
      		frameLeftUpNew.
      copyTo(
      frameOut(rectLeftUp));
     
    
   
    
     
    
    
     
      		frameRightUpNew.
      copyTo(
      frameOut(rectRightUp));
     
    
   
    
     
    
    
     
      		frameLeftDownNew.
      copyTo(
      frameOut(rectLeftDown));
     
    
   
    
     
    
    
     
      		frameRightDownNew.
      copyTo(
      frameOut(rectRightDown));
     
    
   
    
     
    
    
     		
      /*cv::imshow("frameOut.jpg", frameOut);
     
    
   
    
     
    
    
     
       cv::waitKey(0);*/
     
    
   
    
     
    
    
             
      //写入帧图像
     
    
   
    
     
    
    
     
      		writer.
      write(frameOut);
     
    
   
    
     
    
    
     
      	}
     
    
   
    
     
    
    
         
      //释放内存
     
    
   
    
     
    
    
     
      	writer.
      release();
     
    
   
    
     
    
    
     
      	videoLeftUp.
      release();
     
    
   
    
     
    
    
     
      	videoRightUp.
      release();
     
    
   
    
     
    
    
     
      	videoLeftDown.
      release();
     
    
   
    
     
    
    
     
      	videoRightDown.
      release();
     
    
   
    
     
    
    
      
     
    
   
    
     
    
    
     	
      system(
      "pause");
     
    
   
    
     
    
    
     	
      return 
      0;
     
    
   
    
     
    
    
     
      }