1 void my_mouse_callback(int event,int x,int y,int flags,void* param);  2  3 CvRect box;  4  5 bool drawing_box=false;  6  7 // a little subroutine to draw a box on to an image  8 void draw_box(IplImage* img,CvRect rect)  9 {
    10     cvRectangle(img,cvPoint(box.x,box.y),cvPoint(box.x+box.width,box.y+box.height),cvScalar(0xff,0x00)); 11 } 12 13 14 int main(int argc,char** argv) 15 {  16     box=cvRect(-1,-1,0,0); 17 18     IplImage* image =cvCreateImage(cvSize(200,200),IPL_DEPTH_8U,3); 19 20     cvZero(image); 21 22     IplImage* temp =cvCloneImage(image); 23 24     cvNamedWindow("Box example"); 25     cvNamedWindow("image"); 26     cvSetMouseCallback("Box example",my_mouse_callback,(void*) image); 27 28     while(1){
    29         cvCopyImage(image,temp); 30     /*    if(drawing_box) draw_box(image,box); 31         cvShowImage("image",image);*/ 32         if(drawing_box) draw_box(temp,box); 33         cvShowImage("Box example",temp); 34     35         if(cvWaitKey(15)==27) break; 36     } 37 38     cvReleaseImage(&image); 39     cvReleaseImage(&temp); 40     cvDestroyWindow("Box example"); 41     cvDestroyWindow("image"); 42 43     return 0; 44 45     46 } 47 //event 指定鼠标事件类型 48 //int x y 为事件发生时鼠标位置的x,y坐标值。 49 //第四个参数flags 制定了事件在事件发生时的不同状态 50 void my_mouse_callback(int event,int x,int y,int flags,void* param) 51 {
    52     IplImage* image= (IplImage*) param; 53     switch(event) 54     {
    55     case CV_EVENT_MOUSEMOVE: 56         {
    57             if(drawing_box) 58             {
    59                 box.width=x-box.x; 60                 box.height=y-box.y; 61             } 62         } 63         break; 64     case CV_EVENT_LBUTTONDOWN: 65         {
    66             drawing_box=true; 67             box=cvRect(x,y,0,0); 68         } 69         break; 70     case CV_EVENT_LBUTTONUP: 71         {
    72             drawing_box=false; 73             if(box.width<0) 74             {
    75                 box.x=box.x+box.width; 76                 box.width*=-1; 77 78             } 79             if(box.height<0) 80             {
    81                 box.y+=box.height; 82                 box.height*=-1; 83             } 84             draw_box(image,box); 85         } 86         break; 87     } 88 }