Qt WORD/PDF（二）使用 QtPdfium库实现 PDF操作、打印等

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GitHub 源码: QWidgetLearningPro （暂未更新）

姊妹篇: Qt WORD/PDF（一）使用 QtPdfium库实现 PDF 预览

一、简介

QtPdfium 是基于Pdfium库的一个Qt绑定。Pdfium是一个由Google开发并开源的PDF渲染引擎，它被广泛应用于Chrome浏览器和其他一些Google产品中。QtPdfium则是一个专门将Pdfium引入Qt项目的封装，使得Qt应用程序可以使用Pdfium的PDF渲染功能。

它的主要目标是高效的PDF文档渲染，特别是在Web浏览器等高性能需求的应用场景中。相较于Poppler，Pdfium侧重于简洁、高效的渲染和性能优化。

二、演示

在这里插入图片描述

三、代码部分

完整代码

mainwindow.cpp：

#include "mainwindow.h"// #include "ui_mainwindow.h"
#include <QVBoxLayout>
#include <QFileDialog>
#include <QPrinter>
#include <QPrintDialog>
#include <QPainter>
#include <QPrinterInfo>MainWindow::MainWindow(QWidget *parent): QMainWindow(parent)// , ui(new Ui::MainWindow)
{// 设置窗口标题setWindowTitle("PDF Viewer & Printer");this->initWidget();// 主控件和布局QWidget *centralWidget = new QWidget(this);QVBoxLayout *layout = new QVBoxLayout(centralWidget);// PDF 预览区域m_pdfPreview = new QLabel("PDF 预览区域", this);m_pdfPreview->setFixedSize(700, 880);m_pdfPreview->setStyleSheet("border: 1px solid gray; background-color: #f0f0f0;");m_pdfPreview->setAlignment(Qt::AlignCenter);layout->addWidget(m_pdfPreview);//增加一行页码相关，页码控制区域//上一页 当前页/总页码 下一页QHBoxLayout *pageControlLayout = new QHBoxLayout();_prevPageButton = new QPushButton("上一页", this);_pageInfoLabel = new QLabel("0 / 0", this);_nextPageButton = new QPushButton("下一页", this);_pageInfoLabel->setAlignment(Qt::AlignCenter);// 将控件添加到水平布局中pageControlLayout->addWidget(_prevPageButton);pageControlLayout->addWidget(_pageInfoLabel);pageControlLayout->addWidget(_nextPageButton);layout->addLayout(pageControlLayout);// 打印设置区域QHBoxLayout *printerLayout = new QHBoxLayout();m_printerList = new QComboBox(this);m_currentPage = new QRadioButton("当前页", this);m_allPages = new QRadioButton("所有页", this);m_allPages->setChecked(true); // 默认打印所有页m_rangeGroup = new QButtonGroup(this);m_rangeGroup->addButton(m_currentPage);m_rangeGroup->addButton(m_allPages);printerLayout->addWidget(new QLabel("打印机:", this));printerLayout->addWidget(m_printerList);printerLayout->addWidget(m_currentPage);printerLayout->addWidget(m_allPages);layout->addLayout(printerLayout);// 按钮区域QHBoxLayout *buttonLayout = new QHBoxLayout();m_loadButton = new QPushButton("加载PDF", this);m_printButton = new QPushButton("打印PDF", this);buttonLayout->addWidget(m_loadButton);buttonLayout->addWidget(m_printButton);layout->addLayout(buttonLayout);setCentralWidget(centralWidget);// 填充打印机列表populatePrinters();// 信号与槽连接connect(_prevPageButton, &QPushButton::clicked, this, &MainWindow::goToPreviousPage);connect(_nextPageButton, &QPushButton::clicked, this, &MainWindow::goToNextPage);connect(m_loadButton, &QPushButton::clicked, this, &MainWindow::loadPdf);connect(m_printButton, &QPushButton::clicked, this, &MainWindow::printPdf);}MainWindow::~MainWindow()
{m_pdfium = nullptr;delete m_pdfium;
}//初始化界面
void MainWindow::initWidget()
{//初始化变量_currentPage = 0;               // 当前页码_totalPages = 0;                // 总页数
}void MainWindow::populatePrinters()
{// 获取系统打印机列表QList<QPrinterInfo> printers = QPrinterInfo::availablePrinters();for (const QPrinterInfo &printer : printers) {m_printerList->addItem(printer.printerName());}
}//鼠标滚轮事件，放大缩小
void MainWindow::wheelEvent(QWheelEvent *event)
{if(!isPdfValid) {return;}//根据鼠标滚轮的方向来缩放图像const QPoint numDegrees = event->angleDelta() / 8;const int numSteps = numDegrees.y() / 15;if(numSteps != 0){//更新缩放比例if(numSteps > 0) {//放大zoomScale *= 1.1;}else {//缩小,但要确保缩放比例不会小于某个最小值（比如0.1）zoomScale /= 1.1;zoomScale = qMax(zoomScale, 0.3);}//更新缩放后的图像并显示updateScaledPixmap();}
}//更新缩放图像
void MainWindow::updateScaledPixmap()
{//计算缩放后的尺寸QSize scaledSize = _showPixmap.size() * zoomScale;//缩放图像QPixmap scaledPixmap = _showPixmap.scaled(scaledSize,Qt::IgnoreAspectRatio,Qt::SmoothTransformation);//更新QLabel的Pixmapm_pdfPreview->setPixmap(scaledPixmap);
}void MainWindow::loadPdf()
{// 打开文件对话框加载 PDFQString fileName = QFileDialog::getOpenFileName(this, "选择PDF文件", "D:/23_Outproject/32_ZNPicture/Src/QtPdfiumTest2", "PDF Files (*.pdf)");if (fileName.isEmpty()) {isPdfValid = false;return;}m_pdfium = new QPdfium();// 加载 PDF 文件m_pdfium->loadFile(fileName);isPdfValid = m_pdfium->isValid();if (!isPdfValid) {m_pdfPreview->setText("加载PDF失败！");return;}_totalPages = m_pdfium->pageCount(); // 更新总页数_currentPage = 0;                    // 当前页重置为第一页_pageInfoLabel->setText(QString("%1 / %2").arg(_currentPage+1).arg(_totalPages));//预览第一页QPdfiumPage page = m_pdfium->page(_currentPage);if (page.isValid()) {QImage image = page.image(1.0); // 渲染为 QImage_showPixmap = QPixmap::fromImage(image).scaled (m_pdfPreview->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);m_pdfPreview->setPixmap(_showPixmap);}
}//上一页
void MainWindow::goToPreviousPage()
{if (_currentPage > 0) {_currentPage--;_pageInfoLabel->setText(QString("%1 / %2").arg(_currentPage+1).arg(_totalPages));QPdfiumPage page = m_pdfium->page(_currentPage);if (page.isValid()) {QImage image = page.image(1.0);_showPixmap = QPixmap::fromImage(image).scaled (m_pdfPreview->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);m_pdfPreview->setPixmap(_showPixmap);}}
}//下一页
void MainWindow::goToNextPage()
{if (_currentPage < _totalPages-1) {_currentPage++;_pageInfoLabel->setText(QString("%1 / %2").arg(_currentPage+1).arg(_totalPages));QPdfiumPage page = m_pdfium->page(_currentPage);if (page.isValid()) {QImage image = page.image(1.0);_showPixmap = QPixmap::fromImage(image).scaled (m_pdfPreview->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);m_pdfPreview->setPixmap(_showPixmap);}}
}void MainWindow::printPdf()
{// 调用打印功能if (!m_pdfium || !m_pdfium->isValid() || m_pdfium->pageCount() == 0) {m_pdfPreview->setText("未加载有效PDF，无法打印！");return;}// 创建打印机对象QPrinter printer(QPrinter::HighResolution);printer.setPrinterName(m_printerList->currentText());//是用来设置打印页面的方向，指定打印内容的布局是 纵向 (Portrait) 还是 横向 (Landscape)。printer.setOrientation(QPrinter::Portrait);printer.setPageSize(QPrinter::A4);// 设置打印范围int fromPage = 1;int toPage = m_pdfium->pageCount();if (m_currentPage->isChecked()) {fromPage = toPage = 1; // 当前页为第一页}// 打印 PDFQPainter painter(&printer);for (int i = fromPage; i <= toPage; ++i) {QPdfiumPage page = m_pdfium->page(i);if (!page.isValid()) continue;QImage image = page.image(1.0);QRect targetRect = printer.pageRect();QPixmap pixmap = QPixmap::fromImage(image).scaled (targetRect.size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);painter.drawPixmap(0, 0, pixmap);if (i < toPage)printer.newPage();}painter.end();
}

mainwindow.h：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>#include <QFileDialog>
#include <QDesktopServices>
#include <QTime>
#include <QImage>
#include <QPixmap>
#include <QWheelEvent>
#include <QDebug>#include "qpdfium.h"#include <QPrinter>
#include <QPainter>
#include <QPrintDialog>
#include <QFileDialog>//Item
#include <QWheelEvent>
#include <QLabel>
#include <QPushButton>
#include <QComboBox>
#include <QRadioButton>
#include <QPrinter>
#include <QButtonGroup>QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACEclass MainWindow : public QMainWindow
{Q_OBJECTpublic:MainWindow(QWidget *parent = nullptr);~MainWindow();void initWidget();  //         初始化参数void showPdfData(int curPage);void updateScaledPixmap();protected:void wheelEvent(QWheelEvent *event) override;private slots:void goToPreviousPage();       // 上一页槽函数void goToNextPage();           // 下一页槽函数void loadPdf();void printPdf();private:Ui::MainWindow *ui;int m_curPage;                  //当前页int m_totalPage;                //总页数double  zoomScale;              //缩放比例bool    isPdfValid = false;     //打开pdf是否有效QString m_saveImagePath;        //图像保存路径QPixmap _showPixmap;           //界面显示图像//Item1QPushButton *_prevPageButton; // 上一页按钮QPushButton *_nextPageButton; // 下一页按钮QLabel      *_pageInfoLabel;  // 当前页/总页码显示//Item2QPdfium *m_pdfium = nullptr;    //QPdfium对象QLabel *m_pdfPreview;           // 用于显示PDF预览QPushButton *m_loadButton;      // 加载PDF按钮QPushButton *m_printButton;     // 打印按钮//基本参数int _currentPage;               // 当前页码int _totalPages;                // 总页数QComboBox *m_printerList;       // 打印设备列表QRadioButton *m_currentPage;    // 打印范围：当前页QRadioButton *m_allPages;       // 打印范围：所有页QButtonGroup *m_rangeGroup;     // 打印范围按钮组void populatePrinters();        // 获取系统打印机
};
#endif // MAINWINDOW_H