Qt下使用OpenCV的鼠标回调函数进行圆形/矩形/多边形的绘制

---

前言

本文主要讲述了在Qt下使用OpenCV的鼠标回调在OpenCV的namedWindow和imshow函数显示出来的界面上进行一些图形的绘制，并最终将绘制好的图形显示在QLabel上。示例代码见文章内容，大家可以参考学习，如有错误之处，欢迎大家批评指正。

项目效果

---

提示：以下是本篇文章正文内容，下面案例可供参考

一、设置imshow显示窗口

这里对imshow出来的窗口进行了初始化，在namedWindow函数中设置了WINDOW_NORMAL标志，用来允许用户调整窗口大小。

//开始绘制区域
void Widget::startDrawArea(Mat imageMat)
{
    if(imageMat.empty())
    {
        QMessageBox::warning(this,"警告","请先选择显示图像!");
        return;
    }

    //显示绘图窗口
    QString title = "绘制区域";
    string strTitle = title.toLocal8Bit().toStdString();
    namedWindow(strTitle,WINDOW_NORMAL);

    //设置窗口的初始位置和大小
    moveWindow(strTitle,690,290);
    resizeWindow(strTitle,400,400);

    //设置鼠标回调函数
    m_drawMat = getDrawAreaMat();
    setMouseCallback(strTitle,mouseHandler,&imageMat);

    //显示图像并等待用户操作
    imshow(strTitle,m_drawMat);
    waitKey(0);
}

二、绘制圆形

绘制圆形的时候，鼠标左键按下记录当前点位为圆心，按下并移动时记录移动的距离为半径，并作判断确保绘制的圆不会超出图形边界，这里会实时显示绘制的圆形，左键松开时结束圆的绘制。

//绘制圆形
if(m_drawCircleFlag)
{
    m_drawCircleFlag = false;
    Point pt = Point(x,y);
    m_radius = norm(pt - m_center);
    int radiusMax = std::min(m_center.x,resultMat.cols - m_center.x);
    radiusMax = std::min(radiusMax,m_center.y);
    radiusMax = std::min(radiusMax,resultMat.rows - m_center.y);
    if(m_radius > radiusMax)
    {
        m_radius = radiusMax;
    }
    circle(resultMat, m_center, m_radius, Scalar(0, 0, 255), 1, LINE_AA);
    m_drawMat = resultMat.clone();
    imshow(strTitle, m_drawMat);
}

三、绘制矩形

绘制矩形的时候，鼠标左键按下记录当前点位为矩形的起点，按下并移动时记录当前点位为矩形的终点，在移动过程中也会实时显示绘制出来的矩形，左键松开时结束矩形的绘制。

//绘制矩形
if(m_drawRectFlag)
{
    m_drawRectFlag = false;
    m_endPoint = Point(x, y);
    rectangle(resultMat, Rect(m_startPoint,m_endPoint), Scalar(0, 255, 0), 1, LINE_AA);
    m_drawMat = resultMat.clone();
    imshow(strTitle, m_drawMat);
}

四、绘制多边形

多边形需要获取各个顶点，所以这里在每次鼠标左键松开时将当前点保存到多边形顶点容器中，并在获取下一个顶点时将其与前一点相连起来，直到鼠标右键按下，将最后一点与第一点相连，结束多边形的绘制。这里每两点之间的连线使用了line函数，在结束绘制时还可以使用polylines函数，下面代码中有编写。

//绘制多边形
m_drawPolygonFlag = false;
if(m_vPolygon.size() > 2)
{
    //如果已经绘制了多个点,将最后一个点与第一个点连接起来
    line(resultMat, m_vPolygon[0], m_vPolygon.back(), Scalar(255, 0, 0), 1, LINE_AA);

    //或者使用polylines绘制
    //vector> polygons;
    //polygons.push_back(m_vPolygon);
    //polylines(resultMat, polygons, 1, Scalar(255, 0, 0), 1, LINE_AA, 0);

    imshow(strTitle, resultMat);
}

五、示例完整代码

1.MyTest.pro
在这里我将OpenCV库的头文件和库文件打包到了OpenCV文件夹，并放在项目源程序的目录下，然后在pro文件中包含这个路径，代码如下：

#OpenCV
INCLUDEPATH += $$PWD/OpenCV/Includes
DEPENDPATH += $$PWD/OpenCV/Includes
LIBS += -L$$PWD/OpenCV/Lib/ -lopencv_world455

2.widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include 
#include 
#include 
#include 

#include "opencv2/opencv.hpp"

using namespace cv;
using namespace std;

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

    Mat getDrawAreaMat();
    QPixmap cvMatToPixmap(const Mat imageMat);

    void startDrawArea(Mat imageMat);

private:
    static void mouseHandler(int event, int x, int y, int flags, void* param);

private slots:
    void on_pb_selectMat_clicked();
    void on_pb_drawCircle_clicked();
    void on_pb_drawRect_clicked();
    void on_pb_drawPolygon_clicked();

private:
    Ui::Widget *ui;

    Mat m_showMat;   //界面显示图像

};
#endif // WIDGET_H

3.widget.cpp

#include "widget.h"
#include "ui_widget.h"

//全局变量
Mat m_drawMat;   //绘制的图像

bool m_drawCircleFlag = false;    //绘制圆形标志
bool m_drawRectFlag = false;      //绘制矩形标志
bool m_drawPolygonFlag = false;   //绘制多边形标志

int m_radius = 0;               //绘制圆的半径
Point m_center = Point();       //绘制圆的圆心
Point m_startPoint = Point();   //绘制矩形的起点
Point m_endPoint = Point();     //绘制矩形的终点
vector<Point> m_vPolygon;       //多边形的顶点容器

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    this->setFixedSize(650,420);
}

Widget::~Widget()
{
    delete ui;
}

//显示绘制的区域
Mat Widget::getDrawAreaMat()
{
    //绘制圆
    Mat showMat = m_showMat.clone();
    if((m_radius != 0) && (m_center != Point(0,0)))
    {
        circle(showMat, m_center, m_radius, Scalar(0, 0, 255), 1, LINE_AA);
    }

    //绘制矩形
    if((m_startPoint != Point(0,0)) && (m_endPoint != Point(0,0)))
    {
        rectangle(showMat, Rect(m_startPoint,m_endPoint), Scalar(0, 255, 0), 1, LINE_AA);
    }

    //绘制多边形
    int vNum = m_vPolygon.size();
    for(int i=1;i<vNum;i++)
    {
        line(showMat, m_vPolygon[i-1], m_vPolygon[i], Scalar(255, 0, 0), 1, LINE_AA);
        if(i == vNum-1)
        {
            line(showMat, m_vPolygon[0], m_vPolygon.back(), Scalar(255, 0, 0), 1, LINE_AA);
        }
    }
    return showMat;
}

//Mat转QPixmap
QPixmap Widget::cvMatToPixmap(const Mat imageMat)
{
    QImage showImage;
    if(imageMat.channels() > 1)
    {
        showImage = QImage((const unsigned char*)(imageMat.data),imageMat.cols,imageMat.rows,imageMat.step,QImage::Format_RGB888);   //彩色图
    }
    else
    {
        showImage = QImage((const unsigned char*)(imageMat.data),imageMat.cols,imageMat.rows,imageMat.step,QImage::Format_Indexed8);   //灰度图
    }

    //OpenCV使用BGR顺序,而Qt使用RGB顺序,因此需要交换颜色通道
    return QPixmap::fromImage(showImage.rgbSwapped());
}

//开始绘制区域
void Widget::startDrawArea(Mat imageMat)
{
    if(imageMat.empty())
    {
        QMessageBox::warning(this,"警告","请先选择显示图像!");
        return;
    }

    //显示绘图窗口
    QString title = "绘制区域";
    string strTitle = title.toLocal8Bit().toStdString();
    namedWindow(strTitle,WINDOW_NORMAL);

    //设置窗口的初始位置和大小
    moveWindow(strTitle,690,290);
    resizeWindow(strTitle,400,400);

    //设置鼠标回调函数
    m_drawMat = getDrawAreaMat();
    setMouseCallback(strTitle,mouseHandler,&imageMat);

    //显示图像并等待用户操作
    imshow(strTitle,m_drawMat);
    waitKey(0);
}

//鼠标回调函数
void Widget::mouseHandler(int event, int x, int y, int flags, void* param)
{
    QString title = "绘制区域";
    string strTitle = title.toLocal8Bit().toStdString();
    Mat resultMat = *(Mat*)param;
    if(event == EVENT_LBUTTONDOWN)   //鼠标左键按下
    {
        //绘制圆,确定圆心
        if(m_drawCircleFlag)
        {
            m_center = Point(x,y);
        }

        //绘制矩形,确定起点
        if(m_drawRectFlag)
        {
            m_startPoint = Point(x,y);
        }
    }
    else if(event == EVENT_MOUSEMOVE && (flags & EVENT_FLAG_LBUTTON))   //左键按下并移动
    {
        //实时显示绘制的圆
        if(m_drawCircleFlag)
        {
            //计算半径
            Point pt = Point(x,y);
            m_radius = norm(pt - m_center);

            //确保圆不会超出图像边界
            int radiusMax = std::min(m_center.x,resultMat.cols - m_center.x);
            radiusMax = std::min(radiusMax,m_center.y);
            radiusMax = std::min(radiusMax,resultMat.rows - m_center.y);
            if(m_radius > radiusMax)
            {
                m_radius = radiusMax;
            }
            m_drawMat = resultMat.clone();
            circle(m_drawMat, m_center, m_radius, Scalar(0, 0, 255), 1, LINE_AA);
            imshow(strTitle, m_drawMat);
        }

        //实时显示绘制的矩形
        if(m_drawRectFlag)
        {
            m_endPoint = Point(x, y);
            m_drawMat = resultMat.clone();
            rectangle(m_drawMat, Rect(m_startPoint,m_endPoint), Scalar(0, 255, 0), 1, LINE_AA);
            imshow(strTitle, m_drawMat);
        }
    }
    else if(event == EVENT_LBUTTONUP)   //鼠标左键抬起
    {
        //结束绘制圆
        if(m_drawCircleFlag)
        {
            m_drawCircleFlag = false;
            Point pt = Point(x,y);
            m_radius = norm(pt - m_center);
            int radiusMax = std::min(m_center.x,resultMat.cols - m_center.x);
            radiusMax = std::min(radiusMax,m_center.y);
            radiusMax = std::min(radiusMax,resultMat.rows - m_center.y);
            if(m_radius > radiusMax)
            {
                m_radius = radiusMax;
            }
            circle(resultMat, m_center, m_radius, Scalar(0, 0, 255), 1, LINE_AA);
            m_drawMat = resultMat.clone();
            imshow(strTitle, m_drawMat);
        }

        //结束绘制矩形
        if(m_drawRectFlag)
        {
            m_drawRectFlag = false;
            m_endPoint = Point(x, y);
            rectangle(resultMat, Rect(m_startPoint,m_endPoint), Scalar(0, 255, 0), 1, LINE_AA);
            m_drawMat = resultMat.clone();
            imshow(strTitle, m_drawMat);
        }

        //绘制多边形的各顶点
        if(m_drawPolygonFlag)
        {
            m_vPolygon.push_back(Point(x, y));
            for(size_t i = 1; i < m_vPolygon.size(); i++)
            {
                line(resultMat, m_vPolygon[i-1], m_vPolygon[i], Scalar(255, 0, 0), 1, LINE_AA);
            }
            imshow(strTitle, resultMat);
        }
    }
    else if(event == EVENT_RBUTTONDOWN)   //鼠标右键按下
    {
        //结束绘制多边形
        m_drawPolygonFlag = false;
        if(m_vPolygon.size() > 2)
        {
            //如果已经绘制了多个点,将最后一个点与第一个点连接起来
            line(resultMat, m_vPolygon[0], m_vPolygon.back(), Scalar(255, 0, 0), 1, LINE_AA);

            //或者使用polylines绘制
            //vector> polygons;
            //polygons.push_back(m_vPolygon);
            //polylines(resultMat, polygons, 1, Scalar(255, 0, 0), 1, LINE_AA, 0);

            imshow(strTitle, resultMat);
        }
    }
}

//选择图像
void Widget::on_pb_selectMat_clicked()
{
    QString fileName = QFileDialog::getOpenFileName(this,"选择图像文件","E:/PhotoTest/myPhoto","Image Files(*.png *.jpg *.bmp)");
    if(!fileName.isEmpty())
    {
        m_showMat = imread(fileName.toLocal8Bit().toStdString(),1);

        //更新界面显示
        QPixmap showPixmap = cvMatToPixmap(m_showMat);
        if(!showPixmap.isNull())
        {
            ui->lb_showMat->setPixmap(showPixmap.scaled(ui->lb_showMat->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation));   //保持比例
        }
        else
        {
            QMessageBox::warning(this,"警告","图像文件打开失败!");
        }
    }
}

//绘制圆形
void Widget::on_pb_drawCircle_clicked()
{
    setEnabled(false);
    m_drawCircleFlag = true;
    m_drawRectFlag = false;
    m_drawPolygonFlag = false;

    m_radius = 0;
    m_center = Point(0,0);
    startDrawArea(m_showMat.clone());

    //更新界面显示
    QPixmap showPixmap = cvMatToPixmap(getDrawAreaMat());
    if(!showPixmap.isNull())
    {
        ui->lb_showMat->setPixmap(showPixmap.scaled(ui->lb_showMat->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation));
    }
    setEnabled(true);
}

//绘制矩形
void Widget::on_pb_drawRect_clicked()
{
    //点击后禁用窗口交互
    setEnabled(false);
    m_drawCircleFlag = false;
    m_drawRectFlag = true;
    m_drawPolygonFlag = false;

    m_startPoint = Point(0,0);
    m_endPoint = Point(0,0);
    startDrawArea(m_showMat.clone());
    QPixmap showPixmap = cvMatToPixmap(getDrawAreaMat());
    if(!showPixmap.isNull())
    {
        ui->lb_showMat->setPixmap(showPixmap.scaled(ui->lb_showMat->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation));
    }

    //绘制结束后开启交互
    setEnabled(true);
}

//绘制多边形
void Widget::on_pb_drawPolygon_clicked()
{
    setEnabled(false);
    m_drawCircleFlag = false;
    m_drawRectFlag = false;
    m_drawPolygonFlag = true;

    m_vPolygon.clear();
    startDrawArea(m_showMat.clone());
    QPixmap showPixmap = cvMatToPixmap(getDrawAreaMat());
    if(!showPixmap.isNull())
    {
        ui->lb_showMat->setPixmap(showPixmap.scaled(ui->lb_showMat->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation));
    }
    setEnabled(true);
}

4.widget.ui

总结

在Qt下使用OpenCV务必要配置好环境，这样才能正常使用OpenCV的函数。可以看到在这个示例中使用的都是一些基本的函数，但是很好的实现了本文标题所写的功能。在本人之前的文章中，也有使用Qt的事件过滤器来实现这个功能，见下文参考博客。

---

hello：
共同学习，共同进步，如果还有相关问题，可在评论区留言进行讨论。

参考博客：Qt实现在QLabel上显示图片并进行线条/矩形框/多边形的绘制