利用Qt5寫一個簡單的影像瀏覽器－天天向上

參考資料: Image Viewer Example

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自己照著上面範例練習改成Qt5版本, 並支援繁體中文喔!

放大圖片功能

影像縮小功能

原始圖大小

當視窗的尺寸大於圖片, 圖片會自動伸展成一樣大小,即stretch功能

//----------------------------------------------------------------------------------------------------------------------------------------------------------

imageview.h

#ifndef IMAGEVIEWER_H
#define IMAGEVIEWER_H

#include <QMainWindow>
#include <QPrinter>
// #include <QLabel>
// #include <QScrollArea>
// #include <QScrollBar>
// #include <QFileDialog>
// #include <QtGui>
// #include <QMessageBox>
// #include <QAction>
// #include <QPrintDialog>
// #include <QMenu>
// #include <QMenuBar>

class QAction;
class QLabel;
class QMenu;
class QScrollArea;
class QScrollBar;

class ImageViewer : public QMainWindow
{
     Q_OBJECT // 若缺少會顯示 Class declarations lacks Q_OBJECT marco

public:
     ImageViewer(); // 預設constructor

private slots:     // 以下為Callback function宣告(事件處理用)
     void open();
     void print();
     void zoomIn();
     void zoomOut();
     void normalSize();
     void fitToWindow();

private:           // 以下為副程式宣告
     void createActions();
     void createMenus();
     void updateActions();
     void scaleImage(double factor);
     void adjustScrollBar(QScrollBar *scrollBar, double factor);

     QLabel *imageLabel;      // 顯示圖片用
     QScrollArea *scrollArea; // 用來產生scrollbar
     double scaleFactor;      // 縮放比例

#ifndef QT_NO_PRINTER
     QPrinter printer;
#endif
                              // 以下為事件觸發sender
     QAction *openAct;
     QAction *printAct;
     QAction *exitAct;
     QAction *zoomInAct;
     QAction *zoomOutAct;
     QAction *normalSizeAct;
     QAction *fitToWindowAct;
                              // 以下為選單
     QMenu *fileMenu;
     QMenu *viewMenu;
     //QMenu *helpMenu;
};

#endif

//----------------------------------------------------------------------------------------------------------------------------------------------------------
imageview.cpp

#include "imageviewer.h"
#pragma execution_character_set("utf-8") // 繁體中文才不會顯示成亂碼

ImageViewer::ImageViewer()
{
     imageLabel = new QLabel;               // QLabel用來顯示影像
     //imageLabel->setBackgroundRole(QPalette::Base);
     //imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
     imageLabel->setScaledContents(true);    /* stretched 效果,
                                              *如果影像解析度超過畫面範圍會自動縮放, 而不會被砍掉*/

     scrollArea = new QScrollArea;
     //scrollArea->setBackgroundRole(QPalette::Dark);
     scrollArea->setWidget(imageLabel);    // 設定imageLabel為scrollArea的child
     setCentralWidget(scrollArea);         // 設定scrollArea在main Window中間位置

     createActions();                      // 建立Action事件處理
     createMenus();                        // 建立Menu: 建立Menu與Action事件處理的關聯
     QString title = "影像瀏覽器";
     setWindowTitle(title);                // 視窗title
     resize(800, 600);                     // 視窗大小
}
//--------------------------------------------------------------------------

void ImageViewer::open()
{
     QString fileName = QFileDialog::getOpenFileName(this,
                                     "Open File", QDir::currentPath());
     if (!fileName.isEmpty()) {
         QImage image(fileName);          // 載入影像
         if (image.isNull()) {            // 如果無法載入則image為空值(Null)
             QMessageBox::information(this, "影像瀏覽器",
                                      tr("無法載入 %1.").arg(fileName));
             return;
         }
         setWindowTitle(fileName);     // 顯示檔案路徑
         imageLabel->setPixmap(QPixmap::fromImage(image)); // image顯示在imageLabel上
         scaleFactor = 1.0;

         printAct->setEnabled(true);       // printAct致能
         fitToWindowAct->setEnabled(true); // fitToWindowAct致能
         updateActions();

         if (!fitToWindowAct->isChecked())
             imageLabel->adjustSize();
     }
}
//-------------------------------------------------------------

void ImageViewer::print()
{
     Q_ASSERT(imageLabel->pixmap());
#ifndef QT_NO_PRINTER
     QPrintDialog dialog(&printer, this);
     if (dialog.exec()) {
         QPainter painter(&printer);
         QRect rect = painter.viewport();
         QSize size = imageLabel->pixmap()->size();
         size.scale(rect.size(), Qt::KeepAspectRatio);
         painter.setViewport(rect.x(), rect.y(), size.width(), size.height());
         painter.setWindow(imageLabel->pixmap()->rect());
         painter.drawPixmap(0, 0, *imageLabel->pixmap());
     }
#endif
}
//-------------------------------------------------------------

void ImageViewer::zoomIn()
{
     scaleImage(1.25);
}
//-------------------------------------------------------------
void ImageViewer::zoomOut()
{
     scaleImage(0.8);
}
//-------------------------------------------------------------
void ImageViewer::normalSize()
{
     imageLabel->adjustSize();
     scaleFactor = 1.0;
}
//-------------------------------------------------------------

void ImageViewer::fitToWindow()
{
     bool fitToWindow = fitToWindowAct->isChecked(); //判定是否勾選 fitToWindow
     scrollArea->setWidgetResizable(fitToWindow);
     if (!fitToWindow) {
         normalSize();
     }
     updateActions();
}
//-------------------------------------------------------------
void ImageViewer::createActions()
{
     //---------------------------------------------------------
     openAct = new QAction("&Open...", this);      // 開啟事件
     openAct->setShortcut(tr("Ctrl+O"));           // 建立快捷鍵
     //connect(觸發sender,訊號種類,觸發receiver, Callback function)
     connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
     //---------------------------------------------------------
     printAct = new QAction("&Print...", this);
     printAct->setShortcut(tr("Ctrl+P"));
     printAct->setEnabled(false);
     connect(printAct, SIGNAL(triggered()), this, SLOT(print()));
     //---------------------------------------------------------
     exitAct = new QAction(tr("E&xit"), this);
     exitAct->setShortcut(tr("Ctrl+Q"));
     connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
     //---------------------------------------------------------
     zoomInAct = new QAction("Zoom &In (25%)", this);
     zoomInAct->setShortcut(tr("Ctrl++"));
     zoomInAct->setEnabled(false);
     connect(zoomInAct, SIGNAL(triggered()), this, SLOT(zoomIn()));
     //---------------------------------------------------------
     zoomOutAct = new QAction("Zoom &Out (25%)", this);
     zoomOutAct->setShortcut(tr("Ctrl+-"));
     zoomOutAct->setEnabled(false);
     connect(zoomOutAct, SIGNAL(triggered()), this, SLOT(zoomOut()));
     //---------------------------------------------------------
     normalSizeAct = new QAction("&Normal Size", this);
     normalSizeAct->setShortcut(tr("Ctrl+S"));
     normalSizeAct->setEnabled(false);
     connect(normalSizeAct, SIGNAL(triggered()), this, SLOT(normalSize()));
     //---------------------------------------------------------
     fitToWindowAct = new QAction("&Fit to Window", this);
     fitToWindowAct->setEnabled(false);
     fitToWindowAct->setCheckable(true);
     fitToWindowAct->setShortcut(tr("Ctrl+F"));
     connect(fitToWindowAct, SIGNAL(triggered()), this, SLOT(fitToWindow()));
}
//-------------------------------------------------------------
void ImageViewer::createMenus()
{
     fileMenu = new QMenu("檔案", this);   // 新增 fileMenu
     fileMenu->addAction(openAct);        // 加入openAct事件處理
     fileMenu->addAction(printAct);       // 加入printAct事件處理
     fileMenu->addSeparator();            // 加入分隔線
     fileMenu->addAction(exitAct);        // 加入exit事件處理

     viewMenu = new QMenu("瀏覽", this); // 新增 viewMenu
     viewMenu->addAction(zoomInAct);      // 新增zoomInAct事件處理
     viewMenu->addAction(zoomOutAct);     // 新增zoomOutAct事件處理
     viewMenu->addAction(normalSizeAct); // 新增normalSizeAct事件處理
     viewMenu->addSeparator();            // 加入分隔線
     viewMenu->addAction(fitToWindowAct); // 新增fitToWindowAct事件處理

     menuBar()->addMenu(fileMenu);        // 加入fileMenu選單
     menuBar()->addMenu(viewMenu);        // 加入viewMenu選單
}
//-------------------------------------------------------------
void ImageViewer::updateActions()
{
     zoomInAct->setEnabled(!fitToWindowAct->isChecked());
     zoomOutAct->setEnabled(!fitToWindowAct->isChecked());
     normalSizeAct->setEnabled(!fitToWindowAct->isChecked());
}
//-------------------------------------------------------------
void ImageViewer::scaleImage(double factor)
{
     Q_ASSERT(imageLabel->pixmap());
     scaleFactor *= factor;
     imageLabel->resize(scaleFactor * imageLabel->pixmap()->size());

     adjustScrollBar(scrollArea->horizontalScrollBar(), factor);
     adjustScrollBar(scrollArea->verticalScrollBar(), factor);

     zoomInAct->setEnabled(scaleFactor < 3.0);
     zoomOutAct->setEnabled(scaleFactor > 0.333);
}
//-------------------------------------------------------------
void ImageViewer::adjustScrollBar(QScrollBar *scrollBar, double factor)
{
     scrollBar->setValue(int(factor * scrollBar->value()
                             + ((factor - 1) * scrollBar->pageStep()/2)));
}

//----------------------------------------------------------------------------------------------------------------------------------------------------------

imageview.pro

#include "imageviewer.h"
#include <QApplication>

int main(int argc, char *argv[])
{
     QApplication app(argc, argv);
     ImageViewer imageViewer;
     imageViewer.show();
     return app.exec();
}

//----------------------------------------------------------------------------------------------------------------------------------------------------------

imageviewer.pro

QT   += core gui

greaterThan(QT_MAJOR_VERSION, 4) {
    QT += printsupport
}
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

HEADERS       = imageviewer.h
SOURCES       = imageviewer.cpp \
                 main.cpp

# install
TARGET = imageviewer

TEMPLATE = app