Mega Code Archive
Image viewer
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#ifndef IMAGEVIEWER_H
#define IMAGEVIEWER_H
#include <QMainWindow>
#include <QPrinter>
QT_BEGIN_NAMESPACE
class QAction;
class QLabel;
class QMenu;
class QScrollArea;
class QScrollBar;
QT_END_NAMESPACE
class ImageViewer : public QMainWindow
{
Q_OBJECT
public:
ImageViewer();
private slots:
void open();
void print();
void zoomIn();
void zoomOut();
void normalSize();
void fitToWindow();
void about();
private:
void createActions();
void createMenus();
void updateActions();
void scaleImage(double factor);
void adjustScrollBar(QScrollBar *scrollBar, double factor);
QLabel *imageLabel;
QScrollArea *scrollArea;
double scaleFactor;
#ifndef QT_NO_PRINTER
QPrinter printer;
#endif
QAction *openAct;
QAction *printAct;
QAction *exitAct;
QAction *zoomInAct;
QAction *zoomOutAct;
QAction *normalSizeAct;
QAction *fitToWindowAct;
QAction *aboutAct;
QAction *aboutQtAct;
QMenu *fileMenu;
QMenu *viewMenu;
QMenu *helpMenu;
};
#endif
#include <QtGui>
#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();
setWindowTitle(tr("Image Viewer"));
resize(500, 400);
}
void ImageViewer::open()
{
QString fileName = QFileDialog::getOpenFileName(this,
tr("Open File"), QDir::currentPath());
if (!fileName.isEmpty()) {
QImage image(fileName);
if (image.isNull()) {
QMessageBox::information(this, tr("Image Viewer"),
tr("Cannot load %1.").arg(fileName));
return;
}
imageLabel->setPixmap(QPixmap::fromImage(image));
scaleFactor = 1.0;
printAct->setEnabled(true);
fitToWindowAct->setEnabled(true);
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();
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)));
}
#include <QApplication>
#include "imageviewer.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
ImageViewer imageViewer;
imageViewer.show();
return app.exec();
}
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