由于工作需要需要编写一个图片查看器，需要支持鼠标滚动缩放大小，鼠标移动图片位置等，由于无法上传gif，截取的gif示例图暂时不上传了，讲一下大概思路

1 鼠标点击移动图片

    通过重写鼠标点击事件获取到点位，在鼠标移动事件中进行move操作，在paintEvent中指定绘制起始点即可， 与QDialog 移动操作一样，代码如下

//mousePressEvent

void PicShowDlg::mousePressEvent(QMouseEvent *event)

{
  

	QDialog::mousePressEvent(event);

	if (this->rect().contains(event->pos()))

	{
  

		QPoint p(m_pix.rect().x(),m_pix.rect().y());

		QSize size =  m_pix.size();

		m_dPixTempPos = event->globalPos() - m_dPixPos;

	}

}

//鼠标移动事件

void PicShowDlg::mouseMoveEvent(QMouseEvent *event)

{
  

	QDialog::mouseMoveEvent(event);

	if (this->rect().contains(event->pos()))

	{
  

		m_dPixPos = event->globalPos() - m_dPixTempPos;

	}

}

2 放大缩小图片

  通过重写滚轮事件，通过滚动设置比例系数，在paintEvent中重新计算缩放后的图片大小

//鼠标滚轮事件

void PicShowDlg::wheelEvent(QWheelEvent *event)

{
  

    if (event->delta() > 0)

	{
  

		m_rate -= 0.1;

		if (m_rate < 0.018)

			m_rate = 0.01;

	}

	else if (event->delta() < 0 )

	{
  

		m_rate += 0.1;

		if (m_rate >4.5)

		{
  

			m_rate = 5;

		}

	}

	update();

	return QDialog::wheelEvent(event);

}

// paintEvent 事件重新

void PicShowDlg::paintEvent(QPaintEvent *event)

{
  

	QDialog::paintEvent(event);

	QPainter p(this);

	int nH = m_pix.height()*m_rate;

	int nW = m_pix.width()*m_rate;

	QPixmap newPix = m_pix.scaled(nW,nH,Qt::KeepAspectRatio,Qt::SmoothTransformation);

	p.drawPixmap(QRect(m_dPixPos.rx()-(nW - m_pix.width())/2,m_dPixPos.ry()-(nH - m_pix.height())/2, newPix.width(),newPix.height()), newPix);

	update();

}

 

 

picShowDlg类完整代码

.h文件

 

#pragma once

#include <QDialog>

#include <QPixmap>

#include <QPoint>

#include "ui_PicShowDlg.h"

class PicShowDlg:public QDialog

{
  

public:

	explicit PicShowDlg(QWidget *parent = nullptr);

	~PicShowDlg();

	void SetPix(const QPixmap& pix );

	void SetPix(const QString &strFile);

protected:

	virtual void paintEvent(QPaintEvent *event) override;

	virtual void mousePressEvent(QMouseEvent *event) override;

	virtual void mouseMoveEvent(QMouseEvent *event) override;

	virtual void wheelEvent(QWheelEvent *event) override;

	virtual void resizeEvent(QResizeEvent *event) override;

private:

	Ui::PicShowDlg *ui;

	QPixmap m_pix;

	//QRect m_paintRect;

	QPoint m_dPixTempPos;

	QPoint m_dPixPos;

	double m_rate;

};

.cpp文件

#include <QPainter>

#include <QMouseEvent>

#include <QDesktopWidget>

#include "PicShowDlg.h"

PicShowDlg::PicShowDlg(QWidget *parent)

	:QDialog(parent)

	,ui(nullptr)

	, m_rate(1)

{
  

	ui = new Ui::PicShowDlg;

	ui->setupUi(this);

	this->setWindowFlags(this->windowFlags() | Qt::WindowStaysOnTopHint);

	this->setModal(false);

	this->show();

}

PicShowDlg::~PicShowDlg()

{
  

    if(ui != nullptr)

    {
  

        delete ui;

        ui = nullptr;

    }

}

void PicShowDlg::SetPix(const QPixmap& pix)

{
  

	m_pix = pix;

	this->resize(m_pix.size());

}

void PicShowDlg::SetPix(const QString &strFile)

{
  

	m_pix.load(strFile);

	this->setWindowTitle(strFile);

	if (m_pix.height() > QApplication::desktop()->height() -300)

	{
  

		this->resize(m_pix.size() + QSize(300,0));

	}

	else if(m_pix.width() > QApplication::desktop()->width() - 400)

	{
  

		this->resize(m_pix.size() + QSize(0, 200));

	}

	else

	{
  

		this->resize(m_pix.size() + QSize(300, 200));

	}

}

void PicShowDlg::paintEvent(QPaintEvent *event)

{
  

	QDialog::paintEvent(event);

	QPainter p(this);

	int nH = m_pix.height()*m_rate;

	int nW = m_pix.width()*m_rate;

	QPixmap newPix = m_pix.scaled(nW,nH,Qt::KeepAspectRatio,Qt::SmoothTransformation);

	p.drawPixmap(QRect(m_dPixPos.rx()-(nW - m_pix.width())/2,m_dPixPos.ry()-(nH - m_pix.height())/2, newPix.width(),newPix.height()), newPix);

	update();

}

void PicShowDlg::mousePressEvent(QMouseEvent *event)

{
  

	QDialog::mousePressEvent(event);

	if (this->rect().contains(event->pos()))

	{
  

		QPoint p(m_pix.rect().x(),m_pix.rect().y());

		QSize size =  m_pix.size();

		m_dPixTempPos = event->globalPos() - m_dPixPos;

	}

}

void PicShowDlg::mouseMoveEvent(QMouseEvent *event)

{
  

	QDialog::mouseMoveEvent(event);

	if (this->rect().contains(event->pos()))

	{
  

		m_dPixPos = event->globalPos() - m_dPixTempPos;

	}

}

void PicShowDlg::wheelEvent(QWheelEvent *event)

{
  

    if (event->delta() > 0)

	{
  

		m_rate -= 0.1;

		if (m_rate < 0.018)

			m_rate = 0.01;

	}

	else if (event->delta() < 0 )

	{
  

		m_rate += 0.1;

		if (m_rate >4.5)

		{
  

			m_rate = 5;

		}

	}

	update();

	return QDialog::wheelEvent(event);

}

void PicShowDlg::resizeEvent(QResizeEvent *event)

{
  

	this->move((QApplication::desktop()->width() - event->size().width())/2,(QApplication::desktop()->height() - event->size().height())/2);

	m_dPixPos = QPoint((event->size().width() - m_pix.width())/2,(event->size().height() - m_pix.height())/2);

	update();

}

工程代码链接 

https://download.csdn.net/download/i7891090/11975504