Qt 使用Poppler实现pdf阅读器

来源：互联网发布：快手特效软件视频软件编辑：程序博客网时间：2024/06/12 21:49

开发环境 Qt5.5.1、Qt Creator 3.5.1

Qt实现pdf阅读器和MFC实现pdf阅读器，其实原理都是差不多的。

需要用到Poppler开源库，下载地址如下 https://poppler.freedesktop.org/

如果只是要在window的gcc下运行的话，可以下载已经编译好的库 https://sourceforge.net/projects/poppler-win32/

注意：这个是MinGW版本的Qt，也就是运行在GCC环境下的库，里面只包含 *.dll 和 *.a 。如果是Vistual Studio版本的Qt ，那么很不幸里面没有 *.lib文件。

1、新建项目，在项目的根目录新建一个“poppler”文件夹，将poppler中qt5目录下的文件都丢进去（*.h头文件，另外再将编译好的2个*.a文件和2个*.dll丢进去，我这里多丢了实现的*.cc文件，因为*.cc已经被编译成动态库了，所以可以不用包含在代码中）

2、在项目的pro配置文件中添加以下内容，引用poppler的头文件和库文件（注意：我这里是win32，所以前面加了win32前缀）

INCLUDEPATH += $$PWD/poppler

win32: LIBS += -L$$PWD/poppler -llibpoppler

win32: LIBS += -L$$PWD/poppler -llibpoppler-qt5

3、创建pdf工具类（该类负责与poppler库做对接，主要负责获取pdf的总页数，和每页的图像）

（1）pdfutils.h

#ifndef PDFUTILS_H#define PDFUTILS_H#include <QObject>#include <QImage>#include <QSize>#include <QDebug>#include "poppler-qt5.h"class PdfUtils{public:    explicit PdfUtils(QString filePath);    ~PdfUtils();    //获取指定页pdf图像(页码从0开始)    QImage getPdfImage(int pageNumber);    //获取pdf总页码    int getNumPages();    //获取pdf页面大小    QSize getPageSize();private:    QString filePath;    int numPages;    QSize pageSize;    void getPdfInfo();};#endif // PDFUTILS_H

（2）pdfutils.cpp

#include "pdfutils.h"PdfUtils::PdfUtils(QString filePath) {    this->filePath = filePath;    getPdfInfo();}PdfUtils::~PdfUtils() {}QImage PdfUtils::getPdfImage(int pageNumber) {    QImage image;    Poppler::Document* document = Poppler::Document::load(filePath);    if (!document || document->isLocked()) {        // ... error message ....        delete document;        return image;    }    // Document starts at page 0    Poppler::Page* pdfPage = document->page(pageNumber);    if (pdfPage == 0) {        // ... error message ...        return image;    }    // Generate a QImage of the rendered page    image = pdfPage->renderToImage(72, 72, -1, -1, -1, -1);    if (image.isNull()) {        // ... error message ...        return image;    }    // after the usage, the page must be deleted    delete pdfPage;    delete document;    return image;}int PdfUtils::getNumPages() {    return numPages;}QSize PdfUtils::getPageSize() {    return pageSize;}void PdfUtils::getPdfInfo() {    numPages = 0;    Poppler::Document* document = Poppler::Document::load(filePath);    if (!document || document->isLocked()) {        // ... error message ....        delete document;        return;    }    numPages = document->numPages();    Poppler::Page* pdfPage = document->page(0);    pageSize = pdfPage->pageSize();    qDebug()<<pageSize;    delete pdfPage;    delete document;}

4、pdf显示类（pdf的右侧显示滚动条，①拖动滚动条翻页 ②鼠标拖动pdf到最上或最底时翻页）

注意：本文省略了页面缓存，如果是真实的项目的话，本着严谨的态度，请务必缓存页面

（1）mypdfcanvas.h（继承父类的resizeEvent是为了 ①当pdf只有1页时不显示滚动条 ②当用户拖动缩放窗口时动态改变pdf显示尺寸）

#ifndef MYPDFCANVAS_H#define MYPDFCANVAS_H#include <QWidget>#include <QVector>#include <QMouseEvent>#include <QPaintEvent>#include <QPainter>#include <QPaintEvent>#include <QMap>#include <QPalette>#include <QResizeEvent>#include "pdfutils.h"class MyPdfCanvas : public QWidget{    Q_OBJECTpublic:    explicit MyPdfCanvas(QWidget *parent = 0);    ~MyPdfCanvas();    void resizeEvent(QResizeEvent* e);    void paintEvent(QPaintEvent *e);    void mousePressEvent(QMouseEvent *e);    void mouseReleaseEvent(QMouseEvent *e);    void mouseMoveEvent(QMouseEvent *e);    void setMaxCachedNum(int maxCachedNum);    //如果不能解析pdf返回false    bool setPath(QString pdfPath);    //页码从0开始    bool setPage(int pageNumber);    //获取页数    int getNumPages();    float getScaledRatio();    //显示裁剪后的图片    bool showClipImage(int pageNumber, int x, int y, int w, int h);    //取消显示裁剪图片,恢复正常显示    void cancelClip();    //实际获取的pdf宽高度    QSize pdfActualSize;signals:    void pageChanged(int currentPage);private:    PdfUtils* pdfUtils;    QString pdfPath;    //最大缓存图片数量    int maxCachedNum;    //用来缓存pdf的每一个页面的图像(从0开始)    QMap<int, QImage> cachedImageMap;    //用来存储已缓存的pdf页面序号(从0开始)//    QQueue<int> cachedPageQueue;    //当前页码(从0开始)    int currentPage;    //总页码(从0开始)    int numPages;    bool isMouseDown;    int lastMouseY;    //当前pdf页面的图像    QImage image;    int imageX;    int imageY;    int imageMinY;    //是否是剪裁状态    bool isClip;    //获取指定页的图片    bool getPdfImage(int pageNumber);    void reachTop();    void reachBottom();    //判断是否需要发送重定位签名框的信号    void needLocateSignArea();};#endif // MYPDFCANVAS_H

（2）pdfcanvas.cpp

#include "mypdfcanvas.h"MyPdfCanvas::MyPdfCanvas(QWidget *parent) : QWidget(parent) {    pdfUtils = NULL;    imageX = 0;    imageY = 0;    isClip = false;    setAutoFillBackground(true);}MyPdfCanvas::~MyPdfCanvas() {    if(pdfUtils != NULL) delete pdfUtils;}void MyPdfCanvas::resizeEvent(QResizeEvent *e) {    image = this->cachedImageMap[currentPage];    if(!image.isNull()) {        float radio = (float)e->size().width()/(float)e->oldSize().width();        int imageHeight = image.height()* e->size().width()/image.width();        image = image.scaled(e->size().width(), imageHeight);        if(imageHeight < this->height()) {            imageY = (this->height()-imageHeight)/2;            //如果图片高度小于控件高度，则图片居中//            imageMinY = imageY;            imageMinY = 0;            imageY = imageMinY;        } else {            if(radio>0) {                imageY = (int)(imageY*radio);                if(imageY > 0) {                    imageY = 0;                }            } else {                imageY = 0;            }        }    }}void MyPdfCanvas::paintEvent(QPaintEvent *e) {    QPainter* painter = new QPainter(this);    if(image.isNull()) {        painter->fillRect(this->rect(), Qt::transparent);        return;    }    painter->drawImage(0, imageY, image);    delete painter;}void MyPdfCanvas::mousePressEvent(QMouseEvent *e) {    isMouseDown = true;    lastMouseY = e->y();}void MyPdfCanvas::mouseReleaseEvent(QMouseEvent *e){    isMouseDown = false;}void MyPdfCanvas::mouseMoveEvent(QMouseEvent *e){    if(!isMouseDown || image.isNull()) {        return;    }    int distance = e->y() - lastMouseY;    lastMouseY = e->y();    imageY += distance;    if(imageY > 0) {        imageY = 0;        reachTop();        return;    } else if(imageY < imageMinY) {        imageY = imageMinY;        reachBottom();        return;    }    update();}void MyPdfCanvas::setMaxCachedNum(int maxCachedNum) {    this->maxCachedNum = maxCachedNum;}bool MyPdfCanvas::setPath(QString pdfPath) {    this->pdfPath = pdfPath;    if(pdfUtils != NULL) delete pdfUtils;    pdfUtils = new PdfUtils(pdfPath);    numPages = pdfUtils->getNumPages();    if(numPages > 0) {        isClip = false;        pdfActualSize = pdfUtils->getPageSize();    }    cachedImageMap.clear();    currentPage = 0;    imageY = 0;    lastMouseY = 0;    return numPages > 0;}bool MyPdfCanvas::setPage(int pageNumber) {    if(!getPdfImage(pageNumber)) {        return false;    }    isClip = false;    isMouseDown = false;    image = image.scaledToWidth(this->width());    imageMinY = this->height() - image.height();    if(image.height() < this->height()) {        //如果图片高度小于控件高度，则图片居中//        imageMinY /= 2;        imageMinY = 0;        imageY = imageMinY;    } else {        imageY = 0;    }    update();    return true;}int MyPdfCanvas::getNumPages() {    return numPages;}float MyPdfCanvas::getScaledRatio() {    int pdfWidth = pdfUtils->getPageSize().width();    return (float)this->width()/(float)pdfWidth;}bool MyPdfCanvas::showClipImage(int pageNumber, int x, int y, int w, int h) {    if(!getPdfImage(pageNumber)) {        return false;    }    isClip = true;    imageY = 0;    image = image.copy(x, y, w, h).scaled(this->size());    update();}void MyPdfCanvas::cancelClip() {    isClip = false;    setPage(currentPage);}bool MyPdfCanvas::getPdfImage(int pageNumber) {    if(pageNumber<0 || pageNumber >= numPages) {        return false;    }    if(cachedImageMap.contains(pageNumber)) {        image = cachedImageMap.value(pageNumber);    } else {        image = pdfUtils->getPdfImage(pageNumber);        if(!image.isNull()) {            cachedImageMap[pageNumber] = image;            pdfActualSize = image.size();        }    }    if(image.isNull()) {        return false;    }    currentPage = pageNumber;    return true;}void MyPdfCanvas::reachTop() {    if(currentPage > 0) {        emit pageChanged(currentPage-1);    }}void MyPdfCanvas::reachBottom() {    if(currentPage < numPages-1) {        emit pageChanged(currentPage+1);    }}

5、pdf及右侧滑块的装载容器

（1）mainwindow.h

#ifndef MAINWINDOW_H#define MAINWINDOW_H#include <QMainWindow>#include <QScrollBar>#include "mypdfcanvas.h"#define SCROLLBAR_WIDTH 30class MainWindow : public QMainWindow{    Q_OBJECTpublic:    explicit MainWindow(QWidget *parent = 0);    ~MainWindow();    void resizeEvent(QResizeEvent* e);    bool setPdfPath(QString path);    //重新调整pdf界面大小    void resizeCanvas();    void setWidgetVisible(bool pdfCanvasVisible, bool scrollbarVisible);public slots:    //当拖动pdf上滑到顶（或下滑到底）时触发该方法    onPageChange(int currentPage);    //当滑动条的滑块被滑动时，会调用该方法    onScrollBarValueChange();private:    MyPdfCanvas *pdfCanvas;    QScrollBar *scrollbar;};#endif // MAINWINDOW_H

（2）mainwindow.cpp

#include "mainwindow.h"MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) {    pdfCanvas = new MyPdfCanvas(this);    scrollbar = new QScrollBar(Qt::Vertical, this);    setWidgetVisible(false, false);    connect(pdfCanvas, SIGNAL(pageChanged(int)), this, SLOT(onPageChange(int)));    connect(scrollbar, SIGNAL(valueChanged(int)), this, SLOT(onScrollBarValueChange()));}MainWindow::~MainWindow() {}void MainWindow::resizeEvent(QResizeEvent *e) {    resizeCanvas();}bool MainWindow::setPdfPath(QString path) {    bool result = pdfCanvas->setPath(path);    if(result) {        int numPages = pdfCanvas->getNumPages();        if(numPages>1) {            scrollbar->setMaximum(numPages-1);            scrollbar->setValue(0);        }        pdfCanvas->setPage(0);    }    resizeCanvas();    return result;}void MainWindow::resizeCanvas() {    qDebug()<<"resize "<<this->rect()<<", "<<pdfCanvas->rect();    int numPages = pdfCanvas->getNumPages();    if(numPages == 1) {        pdfCanvas->setGeometry(this->rect());        setWidgetVisible(true, false);    } else if(numPages > 1) {        pdfCanvas->setGeometry(0, 0, this->width()-SCROLLBAR_WIDTH, this->height());        scrollbar->setGeometry(this->width()-SCROLLBAR_WIDTH, 0, this->width()-SCROLLBAR_WIDTH, this->height());        setWidgetVisible(true, true);    } else {        //numPages <= 0        setWidgetVisible(false, false);    }}void MainWindow::setWidgetVisible(bool pdfCanvasVisible, bool scrollbarVisible) {    pdfCanvas->setVisible(pdfCanvasVisible);    scrollbar->setVisible(scrollbarVisible);}MainWindow::onPageChange(int currentPage) {    pdfCanvas->setPage(currentPage);}MainWindow::onScrollBarValueChange() {    pdfCanvas->setPage(scrollbar->value());}

6、调用方式

（1）main.cpp

#include "mainwindow.h"#include <QApplication>int main(int argc, char *argv[]){    QApplication a(argc, argv);    MainWindow w;    w.resize(500, 500);    w.show();    QString path = "D://test.pdf";    w.setPdfPath(path);    w.setWindowTitle(path);    return a.exec();}

7、实际效果图

更新于2016-08-03

8、项目下载地址（使用当前最新的库poppler-0.45.0、poppler-0.39.0-win32）

http://download.csdn.net/detail/chy555chy/9593364

该项目在win7（Qt5.1）、win10（Qt5.7）下测试过了，均可正常运行。

下图为项目目录中的poppler文件夹（已经删去所有.cc文件），因为只用库和头文件，Qt便可隐式调用dll中的函数了。

更新于2016-08-22

你们评论中遇到的加载库的时候就奔溃现象我还真没遇到过。

下面是测试情况：

（1）当PDF文件未找到的情况，会输出错误日志，但是并不会崩溃。

（2）当路径中包含”中文“，且包含"空格"的情况，poppler是可以正常打开的。

3 0