学习OpenCV——鼠标事件（画框）

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#include "cv.h"
#include "highgui.h"

bool check_line_state=false;
IplImage* workImg;
IplImage* imgshow;
CvRect ROI_rect;

void on_mouse4(int event, int x,int y,int flags,void* param)
{
    int thickness=2;
    CvPoint p1,p2;
    if(event==CV_EVENT_LBUTTONDOWN)
    {
        //当前鼠标位置（x，y）
        ROI_rect.x=x;
        ROI_rect.y=y;
        check_line_state=true;
    }
    else if(check_line_state&&event==CV_EVENT_MOUSEMOVE)//鼠标状态
    {
        cvCopy(workImg,imgshow);//这一步很重要，不断更新显示图像，不然画出的图像如图2所示
        p1=cvPoint(ROI_rect.x,ROI_rect.y);
        p2=cvPoint(x,y);
        cvRectangle(imgshow,p1,p2,CV_RGB(0,255,150),thickness,CV_AA,0);
        cvShowImage("image",imgshow);

    }
    else if(check_line_state&&event==CV_EVENT_LBUTTONUP)
    {
        check_line_state=false;
        cvWaitKey(20);
    }
}

int main()
{
    workImg=cvLoadImage("D:/Demo.jpg",1);
    imgshow=cvCreateImage(cvSize(workImg->width,workImg->height),workImg->depth,workImg->nChannels);
    cvCopy(workImg,imgshow);
    //cvFlip(imgshow);

    ROI_rect.x=ROI_rect.y=0;
    cvNamedWindow("image",CV_WINDOW_AUTOSIZE);
    cvShowImage("image",imgshow);

    cvSetMouseCallback("image",on_mouse4);

    cvWaitKey();
    cvDestroyWindow("image");
}

图1：                                                                                               图2：

   

from: http://blog.csdn.net/yangtrees/article/details/7573919