imageviewer.cpp Example File

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#include <QtWidgets> #if defined(QT_PRINTSUPPORT_LIB) #include <QtPrintSupport/qtprintsupportglobal.h> #if QT_CONFIG(printdialog) #include <QPrintDialog> #endif #endif #include "imageviewer.h" ImageViewer::ImageViewer() : imageLabel(new QLabel) , scrollArea(new QScrollArea) , scaleFactor(1) { imageLabel->setBackgroundRole(QPalette::Base); imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored); imageLabel->setScaledContents(true); scrollArea->setBackgroundRole(QPalette::Dark); scrollArea->setWidget(imageLabel); scrollArea->setVisible(false); setCentralWidget(scrollArea); createActions(); resize(QGuiApplication::primaryScreen()->availableSize() * 3 / 5); } bool ImageViewer::loadFile(const QString &fileName) { QImageReader reader(fileName); reader.setAutoTransform(true); const QImage newImage =; if (newImage.isNull()) { QMessageBox::information(this, QGuiApplication::applicationDisplayName(), tr("Cannot load %1: %2") .arg(QDir::toNativeSeparators(fileName), reader.errorString())); return false; } setImage(newImage); setWindowFilePath(fileName); const QString message = tr("Opened \"%1\", %2x%3, Depth: %4") .arg(QDir::toNativeSeparators(fileName)).arg(image.width()).arg(image.height()).arg(image.depth()); statusBar()->showMessage(message); return true; } void ImageViewer::setImage(const QImage &newImage) { image = newImage; imageLabel->setPixmap(QPixmap::fromImage(image)); scaleFactor = 1.0; scrollArea->setVisible(true); printAct->setEnabled(true); fitToWindowAct->setEnabled(true); updateActions(); if (!fitToWindowAct->isChecked()) imageLabel->adjustSize(); } bool ImageViewer::saveFile(const QString &fileName) { QImageWriter writer(fileName); if (!writer.write(image)) { QMessageBox::information(this, QGuiApplication::applicationDisplayName(), tr("Cannot write %1: %2") .arg(QDir::toNativeSeparators(fileName)), writer.errorString()); return false; } const QString message = tr("Wrote \"%1\"").arg(QDir::toNativeSeparators(fileName)); statusBar()->showMessage(message); return true; } static void initializeImageFileDialog(QFileDialog &dialog, QFileDialog::AcceptMode acceptMode) { static bool firstDialog = true; if (firstDialog) { firstDialog = false; const QStringList picturesLocations = QStandardPaths::standardLocations(QStandardPaths::PicturesLocation); dialog.setDirectory(picturesLocations.isEmpty() ? QDir::currentPath() : picturesLocations.last()); } QStringList mimeTypeFilters; const QByteArrayList supportedMimeTypes = acceptMode == QFileDialog::AcceptOpen ? QImageReader::supportedMimeTypes() : QImageWriter::supportedMimeTypes(); foreach (const QByteArray &mimeTypeName, supportedMimeTypes) mimeTypeFilters.append(mimeTypeName); mimeTypeFilters.sort(); dialog.setMimeTypeFilters(mimeTypeFilters); dialog.selectMimeTypeFilter("image/jpeg"); if (acceptMode == QFileDialog::AcceptSave) dialog.setDefaultSuffix("jpg"); } void ImageViewer::open() { QFileDialog dialog(this, tr("Open File")); initializeImageFileDialog(dialog, QFileDialog::AcceptOpen); while (dialog.exec() == QDialog::Accepted && !loadFile(dialog.selectedFiles().first())) {} } void ImageViewer::saveAs() { QFileDialog dialog(this, tr("Save File As")); initializeImageFileDialog(dialog, QFileDialog::AcceptSave); while (dialog.exec() == QDialog::Accepted && !saveFile(dialog.selectedFiles().first())) {} } void ImageViewer::print() { Q_ASSERT(imageLabel->pixmap()); #if QT_CONFIG(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::copy() { #ifndef QT_NO_CLIPBOARD QGuiApplication::clipboard()->setImage(image); #endif // !QT_NO_CLIPBOARD } #ifndef QT_NO_CLIPBOARD static QImage clipboardImage() { if (const QMimeData *mimeData = QGuiApplication::clipboard()->mimeData()) { if (mimeData->hasImage()) { const QImage image = qvariant_cast<QImage>(mimeData->imageData()); if (!image.isNull()) return image; } } return QImage(); } #endif // !QT_NO_CLIPBOARD void ImageViewer::paste() { #ifndef QT_NO_CLIPBOARD const QImage newImage = clipboardImage(); if (newImage.isNull()) { statusBar()->showMessage(tr("No image in clipboard")); } else { setImage(newImage); setWindowFilePath(QString()); const QString message = tr("Obtained image from clipboard, %1x%2, Depth: %3") .arg(newImage.width()).arg(newImage.height()).arg(newImage.depth()); statusBar()->showMessage(message); } #endif // !QT_NO_CLIPBOARD } 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() { QMenu *fileMenu = menuBar()->addMenu(tr("&File")); QAction *openAct = fileMenu->addAction(tr("&Open..."), this, &ImageViewer::open); openAct->setShortcut(QKeySequence::Open); saveAsAct = fileMenu->addAction(tr("&Save As..."), this, &ImageViewer::saveAs); saveAsAct->setEnabled(false); printAct = fileMenu->addAction(tr("&Print..."), this, &ImageViewer::print); printAct->setShortcut(QKeySequence::Print); printAct->setEnabled(false); fileMenu->addSeparator(); QAction *exitAct = fileMenu->addAction(tr("E&xit"), this, &QWidget::close); exitAct->setShortcut(tr("Ctrl+Q")); QMenu *editMenu = menuBar()->addMenu(tr("&Edit")); copyAct = editMenu->addAction(tr("&Copy"), this, &ImageViewer::copy); copyAct->setShortcut(QKeySequence::Copy); copyAct->setEnabled(false); QAction *pasteAct = editMenu->addAction(tr("&Paste"), this, &ImageViewer::paste); pasteAct->setShortcut(QKeySequence::Paste); QMenu *viewMenu = menuBar()->addMenu(tr("&View")); zoomInAct = viewMenu->addAction(tr("Zoom &In (25%)"), this, &ImageViewer::zoomIn); zoomInAct->setShortcut(QKeySequence::ZoomIn); zoomInAct->setEnabled(false); zoomOutAct = viewMenu->addAction(tr("Zoom &Out (25%)"), this, &ImageViewer::zoomOut); zoomOutAct->setShortcut(QKeySequence::ZoomOut); zoomOutAct->setEnabled(false); normalSizeAct = viewMenu->addAction(tr("&Normal Size"), this, &ImageViewer::normalSize); normalSizeAct->setShortcut(tr("Ctrl+S")); normalSizeAct->setEnabled(false); viewMenu->addSeparator(); fitToWindowAct = viewMenu->addAction(tr("&Fit to Window"), this, &ImageViewer::fitToWindow); fitToWindowAct->setEnabled(false); fitToWindowAct->setCheckable(true); fitToWindowAct->setShortcut(tr("Ctrl+F")); QMenu *helpMenu = menuBar()->addMenu(tr("&Help")); helpMenu->addAction(tr("&About"), this, &ImageViewer::about); helpMenu->addAction(tr("About &Qt"), &QApplication::aboutQt); } void ImageViewer::updateActions() { saveAsAct->setEnabled(!image.isNull()); copyAct->setEnabled(!image.isNull()); 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))); }

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