头文件

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include <QLabel>
#include <QWheelEvent>
#include <QMouseEvent>
#include <QtDebug>#include <math.h>
#include <QPainter>
#include <QTimer>
#include <QWidget>
#include<QPushButton>namespace Ui {
class MainWindow;
}class MainWindow : public QMainWindow
{Q_OBJECTpublic:explicit MainWindow(QWidget *parent = nullptr);~MainWindow();protected:void wheelEvent(QWheelEvent *event);        // 用鼠标滚轮事件实现图像放大缩小void paintEvent(QPaintEvent *);             //重绘事件void mousePressEvent(QMouseEvent *e);void mouseMoveEvent(QMouseEvent *e);void mouseReleaseEvent(QMouseEvent *e);void OnZoomInImage();void OnZoomOutImage();private:Ui::MainWindow *ui;QString LocalFileName;QImage Image;int X_move;int Y_move;double ZoomValue;QPoint oldPos;bool isPressed;
};class RulerWidget : public QWidget
{
public:RulerWidget(QWidget *parent = nullptr) : QWidget(parent){setMinimumHeight(30); // 设置控件高度setStyleSheet("background-color: #F0F2F5;");}protected:void paintEvent(QPaintEvent *event) override{QPainter painter(this);painter.setRenderHint(QPainter::Antialiasing);int width = this->width();int height = this->height();// 绘制刻度线painter.setPen(Qt::black);for (int i = 0; i <= width; i += 10){bool isLargeTick = (i % 50 == 0); // 每隔50像素绘制一个大刻度线if (isLargeTick){painter.drawLine(i, height - 10, i, height);painter.drawText(i - 10, height - 25, QString::number(i));}else{painter.drawLine(i, height - 5, i, height);}}}
};#endif // MAINWINDOW_H

cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow)
{ui->setupUi(this);LocalFileName = QString(":/img/test.PNG");ZoomValue = 1.0;X_move= 0;Y_move= 0;}MainWindow::~MainWindow()
{delete ui;
}void MainWindow::paintEvent(QPaintEvent *event)
{if(LocalFileName.isNull()){return QWidget::paintEvent(event);}//加载图片if(Image.load(LocalFileName)){QPainter painter(this);//根据窗口计算应该显示的图片的大小int width = qMin(Image.width() , this->width());                                                //返回较小值int height = (width * 1.0)/(Image.width()*1.0 / Image.height());          //width/height图像跟label会根据宽对齐。 height / width则根据长对齐height = qMin(height , this->height());width = height * 1.0 *(Image.width() *1.0 / Image.height());// 平移painter.translate(this->width() / 2 + X_move, this->height() /2 + Y_move);     // int X_move , Y_move ; x y 轴平移的距离// 缩放painter.scale(ZoomValue , ZoomValue);                                          //qreal ZoomValue ；鼠标缩放位置// 绘制图像QRect pecRect(-width / 2 , -height /2 , width , height);              //画显示框  前两个参数是坐标原地(0，0 在label中心) 后两个天参数是长宽painter.drawImage(pecRect , Image);}else{qDebug() << "load failed";}}//鼠标滚轮事件
void MainWindow::wheelEvent(QWheelEvent *event)
{int value = event->delta();if(value > 0)OnZoomInImage();//放大elseOnZoomOutImage();//缩小update();
}void MainWindow::mousePressEvent(QMouseEvent *e)
{oldPos = e->pos();isPressed = true;
}
void MainWindow::mouseMoveEvent(QMouseEvent *e)
{if(!isPressed || ZoomValue==1.0)return QWidget::mouseMoveEvent(e);this->setCursor(Qt::SizeAllCursor);QPoint pos = e->pos();int xPtInterval = pos.x() - oldPos.x();int yPtInterval = pos.y() - oldPos.y();X_move+= xPtInterval;//Y_move+= yPtInterval;oldPos = pos;update();
}void MainWindow::mouseReleaseEvent(QMouseEvent *e)
{Q_UNUSED(e);setCursor(Qt::ArrowCursor);isPressed = false;
}void MainWindow::OnZoomInImage()
{ZoomValue += 0.10;if(ZoomValue >= 5.0){ZoomValue = 5.0;return;}update();
}void MainWindow::OnZoomOutImage()
{ZoomValue -= 0.10;if(ZoomValue <= 1.0){ZoomValue = 1.0;return;}update();
}