1、介绍

实现获取鼠标点击处的图像的坐标和像素值，灰度图显示其灰度值，RGB图显示rgb的值。
OpenCV获取灰度值及彩色像素值的方法：

//灰度图像：
image.at<uchar>(j, i) //j为行数，i为列数
//BGR彩色图像
image.at<Vec3b>(j, i)[0] //B分量
image.at<Vec3b>(j, i)[1] //G分量
image.at<Vec3b>(j, i)[2] //R分量

这里要通过鼠标点击事件来获取鼠标点击的位置和状态，选择OpenCV的setMouseCallback回调函数实现。

2、效果展示

PixelPos_Mouse.PNG

3、代码实现

onMouse.h

#ifndef ONMOUSE_H
#define ONMOUSE_H

#include<iostream>
#include<opencv2/opencv.hpp>

using namespace cv;
using namespace std;

void onMouse(int event, int x, int y, int flags, void* param);  //evnet:鼠标事件类型 x,y:鼠标坐标 flags：鼠标哪个键

void onMouse(int event, int x, int y, int flags, void* param)  //evnet:鼠标事件类型 x,y:鼠标坐标 flags：鼠标哪个键
{
    Mat* im = reinterpret_cast<Mat*>(param);
    switch (event) {

    case EVENT_LBUTTONDOWN:
        //显示图像像素值

        if (static_cast<int>(im->channels()) == 1)
        {
            //若图像为单通道图像，则显示鼠标点击的坐标以及灰度值
            switch (im->type())
            {
            case 0:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<uchar>(Point(x, y))) << endl; break;
            case 1:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<char>(Point(x, y))) << endl; break;
            case 2:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<ushort>(Point(x, y))) << endl; break;
            case 3:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<short>(Point(x, y))) << endl; break;
            case 4:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<int>(Point(x, y))) << endl; break;
            case 5:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<float>(Point(x, y))) << endl; break;
            case 6:
                cout << "at (" << x << ", " << y << " ) value is: " << static_cast<int>(im->at<double>(Point(x, y))) << endl; break;
            }
        }
        else
        {
            //若图像为彩色图像，则显示鼠标点击坐标以及对应的B, G, R值
            cout << "at (" << x << ", " << y << ")"
                 << "  B value is: " << static_cast<int>(im->at<Vec3b>(Point(x, y))[0])
                 << "  G value is: " << static_cast<int>(im->at<Vec3b>(Point(x, y))[1])
                 << "  R value is: " << static_cast<int>(im->at<Vec3b>(Point(x, y))[2])
                 << endl;
        }

        break;
    }
}
#endif // ONMOUSE_H

头文件onMouse.h主要实现鼠标点击事件的回调，输出点击时鼠标的坐标和对应的像素值。

main.cpp

    Mat image1 = imread("lena.png");
    if(image1.empty()){
        qDebug()<<"读取图像错误";
    }
    imshow("image1",image1);

    setMouseCallback("image1", onMouse, reinterpret_cast<void*>(&image1));

这里我用的Qt来实现的，要在pro文件里添加OpenCV库的引用

win32:CONFIG(release, debug|release): LIBS += -LD:/opencv/build/x64/vc15/lib/ -lopencv_world455
else:win32:CONFIG(debug, debug|release): LIBS += -LD:/opencv/build/x64/vc15/lib/ -lopencv_world455d
else:unix: LIBS += -LD:/opencv/build/x64/vc15/lib/ -lopencv_world455

INCLUDEPATH += D:/opencv/build/include
DEPENDPATH += D:/opencv/build/include

4、源码展示

本小例程的代码放到我的开源gitte项目里，欢迎一起学习，也希望能收获你的小星星。
项目源码PixelPos_Mouse