openCV鼠標事件學習

opencv中鼠標事件的學習

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代碼

// MouseOperate.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<iostream>
#include "opencv2/highgui/highgui.hpp"
using namespace std;
using namespace cv;

Rect g_rect;
bool g_ispaint;
void drawRect(Mat &img ,Rect rect); //定義畫矩形函數
void onMousePaint(int event,int x,int y,int flags,void* param);//定義鼠標回調函數
int _tmain(int argc, _TCHAR* argv[])
{
    /*int bb = 20;
    void *a ;
    a = &bb;
    int c;
    int *d = (int*)a;
    cout<<"bb="<<bb<<endl;
    cout<<"*d="<<*d<<endl;
    while(1);
    return 0;
    */

    char *windowName = "衛莊";
    Mat img = imread("D:\\large.png");
    namedWindow(windowName);
    //測試是否讀取成功
//  imshow(windowName,img);
//  waitKey(0);
    //綁定鼠標事件
    setMouseCallback(windowName,onMousePaint,(void*)&img);

    while(1){//循環讀取圖片並顯示
        imshow(windowName,img);
        if(waitKey(10)==27)
            break;
    }
    return 0 ;
}

void onMousePaint(int event,int x,int y,int flags,void* param){
    Mat img = *(Mat*)param;
    switch(event){
    case EVENT_LBUTTONDOWN:
        g_ispaint = true;
        g_rect = Rect(x,y,0,0);
        break;
    case EVENT_MOUSEMOVE:
        if(g_ispaint){
            g_rect.width = x-g_rect.x;
            g_rect.height = y - g_rect.y;
        }

        break;
    case EVENT_LBUTTONUP:
        g_ispaint = false;
        if(g_rect.width<0){
            g_rect.x = g_rect.x+g_rect.width;
            g_rect.width = g_rect.width*-1;
        }
        if(g_rect.height<0){
            g_rect.y+= g_rect.height;
            g_rect.height*=-1;
        }
        drawRect(img,g_rect);
        break;
    }
}
void drawRect(Mat &img ,Rect rect){
    rectangle(img,Point(rect.x,rect.y),Point(rect.x+rect.width,rect.y+rect.height),Scalar::all(255));
}

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細節學習

1.關於void*
void*轉化爲其他類型可以用此思想：先將void*的變量轉換爲需要轉換的類型的指針。然後再解引用即可。如上的* （Mat*）param
2. 回調函數中的x,y爲圖片的座標而非窗口的座標

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