最近在系统的学习opencv的基础知识； 之前没有去系统学习opencv基础，在用opencv的的时候会经常遇到各种问题，很有必要系统学习基础； 好的基础会让后面的学习 和实践 更加顺利；

下面贴出 opencv 鼠标交互的 代码 

#include <opencv2/opencv.hpp>

using namespace cv;

#define WINDONWNAME "画矩形"

void onMouse(int event, int x, int y, int flag, void* );

void DrawRectangle(Mat& img, Rect box);

Rect g_rectangle;

Point ptOrigin;

bool g_bDrawingBox = false;

Mat frame;

int main(int argc, char* argv[])

{

char ch;

VideoCapture cam(0);

if (!cam.isOpened())

{

return -1;

}

namedWindow(WINDONWNAME);

setMouseCallback(WINDONWNAME, onMouse, 0);

while (1)

{

cam>>frame;

DrawRectangle(frame, g_rectangle);

imshow(WINDONWNAME, frame);

ch = waitKey(10);

if (ch == 27)

{

return -1;

}

}

return 0;

}

void onMouse(int event, int x, int y, int flag, void* pagram)

{

switch (event)

{

case EVENT_LBUTTONDOWN:

{

g_bDrawingBox = true;

ptOrigin = Point(x, y);

g_rectangle = Rect(x, y, 0, 0);

break;

}

case EVENT_LBUTTONUP:

{

g_bDrawingBox = false;

break;

}

case EVENT_MOUSEMOVE:

{

if (g_bDrawingBox == true)

{

g_rectangle.x = MIN(ptOrigin.x, x);

g_rectangle.y = MIN(ptOrigin.y, y);

g_rectangle.width = abs(x - ptOrigin.x);

g_rectangle.height = abs(y - ptOrigin.y);

}

}

default:

break;

}

}

void DrawRectangle(Mat& img, Rect Box)

{

rectangle(img, g_rectangle, Scalar(255, 0, 0), 3, 8, 0);

}