Opencv step by step - 鼠标事件

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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\n", box.x,box.y,box.width,box.height);}break;case CV_EVENT_LBUTTONDOWN:draging = true;printf("down evt\n");box.x = x;box.y = y;printf("%d,%d,%d,%d\n", box.x,box.y,box.width,box.height);break;case CV_EVENT_LBUTTONUP:draging = false;printf("%d,%d,%d,%d\n", box.x,box.y,box.width,box.height);box.x = 0;box.y = 0;box.width = 0;box.height  = 0;printf("up evt\n");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：

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