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C++基于QWidget和QLabel实现图片缩放,拉伸与拖拽

作者:随性随笔

这篇文章主要为大家详细介绍了C++如何基于QWidget和QLabel实现图片缩放、拉伸与拖拽等功能,文中的示例代码讲解详细,感兴趣的小伙伴可以跟随小编一起学习一下

最近做ffmpeg视频拉流解码,涉及到截图功能的图片显示操作,特此做记录。

头文件

#ifndef QPICTURESHOT_H
#define QPICTURESHOT_H
 
#include <QWidget>
#include <QLabel>
 
class QPictureShot : public QWidget
{
    Q_OBJECT
 
public:
    explicit QPictureShot(QWidget *parent = nullptr);
 
    ~QPictureShot();
 
 
    //接收一张图片文件路径
    void inputPicFile(QString sFile);
 
    //设置定时消失
    void setAutoDismiss(int nShowSeconds);
 
protected:
 
private:
    //初始化窗体部件
    void InitLayout();
 
    void wheelEvent(QWheelEvent * event) override;
    void resizeEvent(QResizeEvent* event) override ;
    void mousePressEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *event) override;
 
    QLabel *m_pPicLabel;    //图片
    QImage m_image;
    QRect m_initRect;
 
    double opacityValue;//窗体初始化透明度
    float ratio = 1.0f;
    bool m_bLeftPress;//左键按下
    float m_difX;
    float m_difY;
 
 
};
 
#endif // QPICTURESHOT_H

cpp文件:

#include "qpictureshot.h"
#include <QApplication>
#include <QDesktopWidget>
#include <QPainter>
#include <QTimer>
#include <QMouseEvent>
#include <QDebug>
 
 
#ifdef WIN32
#pragma execution_character_set("utf-8")
#endif
 
QPictureShot::QPictureShot(QWidget *parent):
    QWidget(parent),
    m_pPicLabel(new QLabel(this)),
    opacityValue(1.0)
{
    setWindowFlags(Qt::Window  |Qt::WindowTitleHint | Qt::CustomizeWindowHint | Qt::WindowCloseButtonHint | Qt::WindowMaximizeButtonHint);
    setWindowTitle("图片");
    this->setAttribute(Qt::WA_TranslucentBackground);
    InitLayout();
}
 
 
QPictureShot::~QPictureShot()
{
 
}
 
 
//接收一张图片文件路径
void QPictureShot::inputPicFile(QString sFile)
{
    int nPos = sFile.lastIndexOf("/");
    QString sText = sFile.right(sFile.length() - nPos - 1);
    setWindowTitle(sText);
 
    m_image = QImage(sFile);
    if (m_image.isNull())
    {
        m_pPicLabel->setStyleSheet("font-size:18pt;color:white;");
        m_pPicLabel->setAlignment(Qt::AlignCenter);
        m_pPicLabel->setText("文件不存在");
    }
    else
    {
        QPixmap pix = QPixmap::fromImage(m_image);
        pix = pix.scaled(m_pPicLabel->width(), m_pPicLabel->height(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
 
        m_pPicLabel->setScaledContents(true);
        m_pPicLabel->setPixmap(pix);
    }
 
}
 
//设置定时消失
void QPictureShot::setAutoDismiss(int nShowSeconds)
{
    QTimer *mtimer = new QTimer(this);//隐藏的定时器
    mtimer->setTimerType(Qt::PreciseTimer);
    connect(mtimer,&QTimer::timeout,this,[=](){
        if(opacityValue<=0){ this->close(); }
        opacityValue = opacityValue-0.1;
        this->setWindowOpacity(opacityValue);    //设置窗口透明度
        });
 
 
    QTimer *mShowtimer = new QTimer(this);//显示时间的定时器
    mShowtimer->setTimerType(Qt::PreciseTimer);// 修改定时器对象的精度
    connect(mShowtimer,&QTimer::timeout,this,[=](){
        mtimer->start(100);//执行延时自动关闭
        });
    mShowtimer->start(nShowSeconds);
}
//初始化窗体部件
void QPictureShot::InitLayout()
{
    //设置部件大小
    QDesktopWidget* desktop = QApplication::desktop(); // =qApp->desktop();也可以
    this->resize(desktop->width() * 0.8, desktop->height() * 0.8);
    m_pPicLabel->setGeometry(0, 0, desktop->width() * 0.8, desktop->height() * 0.8);
    m_pPicLabel->setCursor(QCursor(Qt::PointingHandCursor));
    m_initRect = this->rect();
 
}
 
void QPictureShot::wheelEvent(QWheelEvent * event)
{ 
    if (m_image.isNull()) return;
 
    QPoint numDegrees = event->angleDelta() / 120;
    float ratio_temp =  (1 + numDegrees.y() / 20.0);
    ratio *= ratio_temp;//在当前的比例基础上乘以
    if (ratio > 3 || ratio < 0.05) return;
 
    int w = ratio_temp*m_pPicLabel->width(); //显示宽度
    int h = ratio_temp*m_pPicLabel->height(); //显示高度
 
    QPoint mousePos = event->pos();
    QPoint picPos = m_pPicLabel->pos();
    int pageWidth = mousePos.x() - picPos.x();
    int pageHeight = mousePos.y() - picPos.y();
 
 
    QPixmap pix = QPixmap::fromImage(m_image);
    pix = pix.scaled(w, h, Qt::IgnoreAspectRatio, Qt::SmoothTransformation); //图像缩放到指定高度和宽度,保持长宽比例
 
    m_pPicLabel->setScaledContents(true);
    m_pPicLabel->setPixmap(pix);
 
    int nMoveX =  pageWidth * (numDegrees.y() / 20.0);
    int nMoveY =  pageHeight * (numDegrees.y() / 20.0);
    m_pPicLabel->setGeometry(m_pPicLabel->pos().x() - nMoveX, m_pPicLabel->pos().y() - nMoveY, w, h);
 
 
}
 
void QPictureShot::mousePressEvent(QMouseEvent *event)
{
    if(event->buttons() & Qt::LeftButton)
    {
        m_bLeftPress = true;
        m_difX = event->pos().x() - m_pPicLabel->x();
        m_difY = event->pos().y() - m_pPicLabel->y();
    }
}
void QPictureShot::mouseMoveEvent(QMouseEvent *event)
{
    if (m_bLeftPress)
    {
        int x = event->pos().x() - m_difX;
        int y = event->pos().y() - m_difY;
        m_pPicLabel->move(x, y);
    }
}
void QPictureShot::mouseReleaseEvent(QMouseEvent *event)
{
    Q_UNUSED(event);
    m_bLeftPress = false;
}
 
 
 
void QPictureShot::resizeEvent(QResizeEvent* event) {
    // 在此处添加对窗口拉伸事件的处理逻辑
    // 输出新的大小信息
    qDebug("New size: %dx%d", width(), height());
 
    float x_ratio = width() * 1.0 / m_initRect.width();
    float y_ratio = height() * 1.0 / m_initRect.height();
 
    m_pPicLabel->setGeometry(m_pPicLabel->x() * x_ratio, m_pPicLabel->y() * y_ratio,  m_pPicLabel->width() * x_ratio, m_pPicLabel->height() * y_ratio);
    if (!m_image.isNull())
    { 
        QPixmap pix = QPixmap::fromImage(m_image);
        pix = pix.scaled(this->width(), this->height(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
 
        m_pPicLabel->setScaledContents(true);
        m_pPicLabel->setPixmap(pix);
    }
 
    m_initRect = this->rect();
    // 调用基类的resizeEvent()函数,确保默认行为也得到执行
    QWidget::resizeEvent(event);
}

测试入口代码

QPictureShot *pic = new QPictureShot(this);
    pic->inputPicFile(":/bg.png");
    pic->show();

到此这篇关于C++基于QWidget和QLabel实现图片缩放,拉伸与拖拽的文章就介绍到这了,更多相关C++图片缩放拉伸与拖拽内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家!

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