OpenCV 接收鼠标消息——用鼠标画长方形

OpenCV 接收鼠标消息——用鼠标画长方形

创建一幅黑色的图像，显示后，用鼠标在显示窗口中，拖动以画出长方形：

 #include "stdafx.h"

 #include <cv.h>
 #include <cxcore.h>
 #include <highgui.h>

 void myMouseCallBack(int event, int x, int y, int flags, void * param);
 CvRect box;
 bool drawing_box = false;
 void draw_box(IplImage * img, CvRect rect)
 {
     cvRectangle(
         img,
         cvPoint(box.x, box.y),
         cvPoint(box.x + box.width, box.y + box.height),
         cvScalar(0x00, 0x00, 0xff)
         );
 }

 int _tmain(int argc, _TCHAR* argv[])
 {
     box = cvRect(-1, -1, 0, 0);

     IplImage * image = cvCreateImage(cvSize(200,200), IPL_DEPTH_8U, 3);

     cvZero(image);

     IplImage * temp = cvCloneImage(image);//会重新分配内存空间

     cvNamedWindow("Box Example");

     cvSetMouseCallback("Box Example", myMouseCallBack, (void*)image);

     while(1)
     {
         cvCopyImage(image, temp);//只是复制值，不会分配新空间
         if(drawing_box)
             draw_box(temp,box);

         cvShowImage("Box Example", temp);
         if(cvWaitKey(15) == 27)
             break;
     }

     cvReleaseImage(&image);
     cvReleaseImage(&temp);
     cvDestroyWindow("Box Example");

     return 0;
 }


 void myMouseCallBack(int event, int x, int y, int flags, void * param)
 {
     IplImage * image = (IplImage*)param;

     switch(event)
     {
     case CV_EVENT_MOUSEMOVE:
         {
             if(drawing_box)
             {
                 box.width = x - box.x;
                 box.height = y - box.y;
             }
         }
         break;
     case CV_EVENT_LBUTTONDOWN:
         {
             drawing_box = true;
             box = cvRect(x,y,0,0);
         }
         break;
     case CV_EVENT_LBUTTONUP:
         {
             drawing_box = false;
             if(box.width < 0)
             {
                 box.x += box.width;
                 box.width *= -1;
             }
             if(box.height < 0)
             {
                 box.y += box.height;
                 box.height *= -1;
             }
             draw_box(image,box);
         }
         break;
     }

 }

结果：