Qt 使用Poppler實現pdf閱讀器的示例代碼

2020-01-26 13:48:09

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開發環境 Qt5.5.1、Qt Creator 3.5.1

Qt實現pdf閱讀器和MFC實現pdf閱讀器，其實原理都是差不多的。

需要用到Poppler開源庫，下載地址如下 https://poppler.freedesktop.org/

如果只是要在window的gcc下運行的話，可以下載已經編譯好的庫 https://sourceforge.net/projects/poppler-win32/

注意：這個是MinGW版本的Qt，也就是運行在GCC環境下的庫，里面只包含 *.dll 和 *.a 。如果是Vistual Studio版本的Qt ，那么很不幸里面沒有 *.lib文件。

1、新建項目，在項目的根目錄新建一個“poppler”文件夾，將poppler中qt5目錄下的文件都丟進去（*.h頭文件，另外再將編譯好的2個*.a文件和2個*.dll丟進去，我這里多丟了實現的*.cc文件，因為*.cc已經被編譯成動態庫了，所以可以不用包含在代碼中）

2、在項目的pro配置文件中添加以下內容，引用poppler的頭文件和庫文件（注意：我這里是win32，所以前面加了win32前綴）

INCLUDEPATH += $$PWD/popplerwin32: LIBS += -L$$PWD/poppler -llibpopplerwin32: LIBS += -L$$PWD/poppler -llibpoppler-qt5

3、創建pdf工具類（該類負責與poppler庫做對接，主要負責獲取pdf的總頁數，和每頁的圖像）

（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();  //獲取指定頁pdf圖像(頁碼從0開始)  QImage getPdfImage(int pageNumber);  //獲取pdf總頁碼  int getNumPages();  //獲取pdf頁面大小  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顯示類（pdf的右側顯示滾動條，①拖動滾動條翻頁 ②鼠標拖動pdf到最上或最底時翻頁）

注意：本文省略了頁面緩存，如果是真實的項目的話，本著嚴謹的態度，請務必緩存頁面

（1）mypdfcanvas.h（繼承父類的resizeEvent是為了 ①當pdf只有1頁時不顯示滾動條 ②當用戶拖動縮放窗口時動態改變pdf顯示尺寸）

#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);  //頁碼從0開始  bool setPage(int pageNumber);  //獲取頁數  int getNumPages();  float getScaledRatio();  //顯示裁剪后的圖片  bool showClipImage(int pageNumber, int x, int y, int w, int h);  //取消顯示裁剪圖片,恢復正常顯示  void cancelClip();  //實際獲取的pdf寬高度  QSize pdfActualSize;signals:  void pageChanged(int currentPage);private:  PdfUtils* pdfUtils;  QString pdfPath;  //最大緩存圖片數量  int maxCachedNum;  //用來緩存pdf的每一個頁面的圖像(從0開始)  QMap<int, QImage> cachedImageMap;  //用來存儲已緩存的pdf頁面序號(從0開始)//  QQueue<int> cachedPageQueue;  //當前頁碼(從0開始)  int currentPage;  //總頁碼(從0開始)  int numPages;  bool isMouseDown;  int lastMouseY;  //當前pdf頁面的圖像  QImage image;  int imageX;  int imageY;  int imageMinY;  //是否是剪裁狀態  bool isClip;  //獲取指定頁的圖片  bool getPdfImage(int pageNumber);  void reachTop();  void reachBottom();  //判斷是否需要發送重定位簽名框的信號  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;      //如果圖片高度小于控件高度，則圖片居中//      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()) {    //如果圖片高度小于控件高度，則圖片居中//    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及右側滑塊的裝載容器

（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);  //重新調整pdf界面大小  void resizeCanvas();  void setWidgetVisible(bool pdfCanvasVisible, bool scrollbarVisible);public slots:  //當拖動pdf上滑到頂（或下滑到底）時觸發該方法  onPageChange(int currentPage);  //當滑動條的滑塊被滑動時，會調用該方法  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、調用方式

（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、實際效果圖