#include <opencv2/opencv.hpp>
using namespace cv;

#define WINDOW_NAME "【程序窗口】"        //為窗口標題定義的宏 


Rect g_rectangle;
bool g_bDrawingBox = false;//是否進行繪制
RNG g_rng(12345);


void on_MouseHandle(int event, int x, int y, int flags, void* param)
{

    Mat& image = *(cv::Mat*) param;
    
 
switch( event)
    {
        //鼠標移動消息
        case EVENT_MOUSEMOVE: 
        {
            if( g_bDrawingBox )//如果是否進行繪制的標識符為真，則記錄下長和寬到RECT型變量中
            {
                g_rectangle.width = x-g_rectangle.x;
                g_rectangle.height = y-g_rectangle.y;
            }
        }
        
 
break;

        //左鍵按下消息
        case EVENT_LBUTTONDOWN: 
        {
            g_bDrawingBox = true;
            g_rectangle =Rect( x, y, 0, 0 );//記錄起始點
        }
        break;

        //左鍵擡起消息
        case EVENT_LBUTTONUP: 
        {
            g_bDrawingBox = false;//置標識符為false
            
 
//對寬和高小於0的處理
            if( g_rectangle.width < 0 )
            {
                g_rectangle.x += g_rectangle.width;
                g_rectangle.width *= -1;
            }

            if( g_rectangle.height < 0 ) 
            {
                g_rectangle.y += g_rectangle.height;
                g_rectangle.height *= -1;
            }
            //調用函數進行繪制
            DrawRectangle( image, g_rectangle );
        }
        break;
    }
}


void DrawRectangle( cv::Mat& img, cv::Rect box )
{
    cv::rectangle(    img,
                    box.tl(),
                    box.br(),
                    cv::Scalar(    g_rng.uniform(0, 255), 
                                g_rng.uniform(0,255), 
                                g_rng.uniform(0,255)
                                )
                );//隨機顏色
}


int main( int argc, char** argv ) 
{

    //【1】準備參數
    g_rectangle = Rect(-1, -1, 0, 0);
    Mat srcImage(600, 800, CV_8UC3), tempImage;
    srcImage.copyTo(tempImage);
    g_rectangle = Rect(-1, -1, 0, 0);
    srcImage = Scalar::all(0);

    //【2】設置鼠標操作回調函數
    namedWindow( WINDOW_NAME );
    setMouseCallback(WINDOW_NAME, on_MouseHandle, (void*)&srcImage);

    //【3】程序主循環，當進行繪制的標識符為真時，進行繪制
    while(1)
    {
        srcImage.copyTo(tempImage);//拷貝源圖到臨時變量
        
        if( g_bDrawingBox )
            DrawRectangle( tempImage, g_rectangle );//當進行繪制的標識符為真，則進行繪制
        
        imshow( WINDOW_NAME, tempImage );
        
        if( waitKey( 10 ) == 27 )
            break;//按下ESC鍵，程序退出
    }
    return 0;
}

opencv 鼠標操作