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

using namespace cv;
using namespace std;
/***********	回撥函式宣告	****************/
void my_mouse_callback(int event, int x, int y, int flags, void* param);

CvRect box;
bool drawing_box = false;
////////繪製矩形函式////////////////
void draw_box(IplImage* img, CvRect rect)
{
	cvRectangle(img, cvPoint(box.x, box.y), cvPoint(box.x + box.width, box.y + box.height),
		cvScalar(0xff, 0x00, 0x00));
}

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

	IplImage* image = cvCreateImage(cvSize(200, 200),
		IPL_DEPTH_8U, 3);
	/*******把影象清零**********/
	cvZero(image);
	IplImage* temp = cvCloneImage(image);	//複製影象

	cvNamedWindow("Box Example");			//建立視窗
	/****************	註冊回撥函式到OpenCV中	***********************/
	cvSetMouseCallback("Box Example", my_mouse_callback, (void *)image);

	while (1)
	{
		cvCopyImage(image, temp);		//將image資料複製到temp中
		if (drawing_box)
			draw_box(temp, box);		//在temp中繪製矩形
		cvShowImage("Box Example", temp);	//在Box Example視窗中顯示繪製的矩形

		if (cvWaitKey(15) == 27)
			break;

	}
}

void my_mouse_callback(int event, int x, int y, int flags, void* param)
{
	//將註冊回撥函式中的引數（void*）param恢復並儲存到image中
	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;

	}

}