Opencv step by step

鼠标事件有下面几种（没有滚轮事件，比较遗憾）：

#define CV_EVENT_MOUSEMOVE 0                   滑动
#define CV_EVENT_LBUTTONDOWN 1           左键点击
#define CV_EVENT_RBUTTONDOWN 2           右键点击
#define CV_EVENT_MBUTTONDOWN 3           中键点击
#define CV_EVENT_LBUTTONUP 4                 左键放开
#define CV_EVENT_RBUTTONUP 5                 右键放开
#define CV_EVENT_MBUTTONUP 6                 中键放开
#define CV_EVENT_LBUTTONDBLCLK 7         左键双击
#define CV_EVENT_RBUTTONDBLCLK 8         右键双击
#define CV_EVENT_MBUTTONDBLCLK 9         中键双击

下面用一个例子来学习一下这个事件：

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

CvRect box;
bool draging;

void mouse_callback(int event, int x, int y, int flags, void* param)
{
	IplImage *image = (IplImage*)param;
	switch(event) {
	case CV_EVENT_MOUSEMOVE:
		if(draging) {
			box.width = x - box.x;
			box.height = y - box.y;
			//printf("%d,%d,%d,%d
", box.x,box.y,box.width,box.height);
		}
	break;
	case CV_EVENT_LBUTTONDOWN:
		draging = true;
		printf("down evt
");
		box.x = x;
		box.y = y;
		printf("%d,%d,%d,%d
", box.x,box.y,box.width,box.height);
	break;
	case CV_EVENT_LBUTTONUP:
		draging = false;
		printf("%d,%d,%d,%d
", box.x,box.y,box.width,box.height);
		box.x = 0;
		box.y = 0;
		box.width = 0;
		box.height  = 0;
		printf("up evt
");	
	break;



	}

	

}


int main(int argc, char **argv)
{
	const char* window_name = "my mouse";


	box =  cvRect(-1, -1, 0, 0);
	IplImage *image = cvCreateImage(cvSize(200,200), 8, 3);
	cvZero(image);


	cvNamedWindow(window_name);
	cvSetMouseCallback(window_name, mouse_callback, (void *)image);
	cvShowImage(window_name, image);


	while(1) {
		if(draging) {
			cvZero(image);
			cvRectangle(image,cvPoint(box.x,box.y),
				cvPoint(box.x + box.width ,box.y+box.height),
				cvScalar(255,255,0));
			cvShowImage(window_name, image);
		}
			
		if(cvWaitKey(10) == 27)
			break;
	}

	cvReleaseImage(&image);
	cvDestroyWindow(window_name);


}

这个例子的效果实际上是在鼠标拖动的时候画矩形。核心点就是回调函数了：

 cvSetMouseCallback(window_name, mouse_callback, (void *)image);

cvWaitKey是一个非阻塞的过程，所以拖动的时候下面的代码一直会被调用：

			cvZero(image);
			cvRectangle(image,cvPoint(box.x,box.y),
				cvPoint(box.x + box.width ,box.y+box.height),
				cvScalar(255,255,0));
			cvShowImage(window_name, image);

这就是刷新的过程了。

下面是效果图：