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#include <QtWidgets>
#ifndef QT_NO_PRINTER
#include <QPrintDialog>
#endif

#include "imageviewer.h"

ImageViewer::ImageViewer()
{
    imageLabel = new QLabel;
    imageLabel->setBackgroundRole(QPalette::Base);
    imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
    imageLabel->setScaledContents(true);

    scrollArea = new QScrollArea;
    scrollArea->setBackgroundRole(QPalette::Dark);
    scrollArea->setWidget(imageLabel);
    setCentralWidget(scrollArea);

    createActions();
    createMenus();

    resize(QGuiApplication::primaryScreen()->availableSize() * 3 / 5);
}


bool ImageViewer::loadFile(const QString &fileName)
{
    QImage image(fileName);
    if (image.isNull()) {
        QMessageBox::information(this, QGuiApplication::applicationDisplayName(),
                                 tr("Cannot load %1.").arg(QDir::toNativeSeparators(fileName)));
        setWindowFilePath(QString());
        imageLabel->setPixmap(QPixmap());
        imageLabel->adjustSize();
        return false;
    }
    imageLabel->setPixmap(QPixmap::fromImage(image));
    scaleFactor = 1.0;

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

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

    setWindowFilePath(fileName);
    return true;
}



void ImageViewer::open()
{
    QStringList mimeTypeFilters;
    foreach (const QByteArray &mimeTypeName, QImageReader::supportedMimeTypes())
        mimeTypeFilters.append(mimeTypeName);
    mimeTypeFilters.sort();
    const QStringList picturesLocations = QStandardPaths::standardLocations(QStandardPaths::PicturesLocation);
    QFileDialog dialog(this, tr("Open File"),
                       picturesLocations.isEmpty() ? QDir::currentPath() : picturesLocations.first());
    dialog.setAcceptMode(QFileDialog::AcceptOpen);
    dialog.setMimeTypeFilters(mimeTypeFilters);
    dialog.selectMimeTypeFilter("image/jpeg");

    while (dialog.exec() == QDialog::Accepted && !loadFile(dialog.selectedFiles().first())) {}
}

void ImageViewer::print()
{
    Q_ASSERT(imageLabel->pixmap());
#if !defined(QT_NO_PRINTER) && !defined(QT_NO_PRINTDIALOG)
    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();
    scrollArea->setWidgetResizable(fitToWindow);
    if (!fitToWindow) {
        normalSize();
    }
    updateActions();
}

void ImageViewer::about()
{
    QMessageBox::about(this, tr("About Image Viewer"),
            tr("<p>The <b>Image Viewer</b> example shows how to combine QLabel "
               "and QScrollArea to display an image. QLabel is typically used "
               "for displaying a text, but it can also display an image. "
               "QScrollArea provides a scrolling view around another widget. "
               "If the child widget exceeds the size of the frame, QScrollArea "
               "automatically provides scroll bars. </p><p>The example "
               "demonstrates how QLabel's ability to scale its contents "
               "(QLabel::scaledContents), and QScrollArea's ability to "
               "automatically resize its contents "
               "(QScrollArea::widgetResizable), can be used to implement "
               "zooming and scaling features. </p><p>In addition the example "
               "shows how to use QPainter to print an image.</p>"));
}

void ImageViewer::createActions()
{
    openAct = new QAction(tr("&Open..."), this);
    openAct->setShortcut(tr("Ctrl+O"));
    connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

    printAct = new QAction(tr("&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(tr("Zoom &In (25%)"), this);
    zoomInAct->setShortcut(tr("Ctrl++"));
    zoomInAct->setEnabled(false);
    connect(zoomInAct, SIGNAL(triggered()), this, SLOT(zoomIn()));

    zoomOutAct = new QAction(tr("Zoom &Out (25%)"), this);
    zoomOutAct->setShortcut(tr("Ctrl+-"));
    zoomOutAct->setEnabled(false);
    connect(zoomOutAct, SIGNAL(triggered()), this, SLOT(zoomOut()));

    normalSizeAct = new QAction(tr("&Normal Size"), this);
    normalSizeAct->setShortcut(tr("Ctrl+S"));
    normalSizeAct->setEnabled(false);
    connect(normalSizeAct, SIGNAL(triggered()), this, SLOT(normalSize()));

    fitToWindowAct = new QAction(tr("&Fit to Window"), this);
    fitToWindowAct->setEnabled(false);
    fitToWindowAct->setCheckable(true);
    fitToWindowAct->setShortcut(tr("Ctrl+F"));
    connect(fitToWindowAct, SIGNAL(triggered()), this, SLOT(fitToWindow()));

    aboutAct = new QAction(tr("&About"), this);
    connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

    aboutQtAct = new QAction(tr("About &Qt"), this);
    connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
}

void ImageViewer::createMenus()
{
    fileMenu = new QMenu(tr("&File"), this);
    fileMenu->addAction(openAct);
    fileMenu->addAction(printAct);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAct);

    viewMenu = new QMenu(tr("&View"), this);
    viewMenu->addAction(zoomInAct);
    viewMenu->addAction(zoomOutAct);
    viewMenu->addAction(normalSizeAct);
    viewMenu->addSeparator();
    viewMenu->addAction(fitToWindowAct);

    helpMenu = new QMenu(tr("&Help"), this);
    helpMenu->addAction(aboutAct);
    helpMenu->addAction(aboutQtAct);

    menuBar()->addMenu(fileMenu);
    menuBar()->addMenu(viewMenu);
    menuBar()->addMenu(helpMenu);
}

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)));
}