Image viewer:

src/plugins/imageviewer/QImageViewer.cpp

@@ -0,0 +1,193 @@
+#include "QImageViewer.h"
+#include <QtWidgets/QScrollBar>
+#include <QtWidgets/QVBoxLayout>
+#include <QtWidgets/QFileDialog>
+#include <QtGui/QImageReader>
+#include <QtGui/QImageWriter>
+#include <QtGui/QPainter>
+#include <QtCore/QDebug>
+#include <QtPrintSupport/QPrintDialog>
+
+//
+// https://doc.qt.io/qt-5/qtwidgets-widgets-imageviewer-example.html
+// https://stackoverflow.com/questions/53193010/how-to-resize-a-qlabel-with-pixmap-inside-a-qscrollarea
+//
+
+QImageViewer::QImageViewer (QWidget* parent) : QWidget(parent) {
+
+    _zoomFactor = 1.0;
+
+    // Setup the widgets
+    QVBoxLayout* layout = new QVBoxLayout(this);
+    layout->setContentsMargins(0, 0, 0, 0);
+
+    _imageLabel = new QLabel();
+    _imageLabel->setBackgroundRole(QPalette::Base);
+    _imageLabel->setScaledContents(true);
+
+    _scrollArea = new QScrollArea(this);
+    _scrollArea->setBackgroundRole(QPalette::Dark);
+    _scrollArea->setWidget(_imageLabel);
+    _scrollArea->setWidgetResizable(false);
+
+    layout->addWidget(_scrollArea);
+
+    _imageLabel->setPixmap(QPixmap::fromImage(_image));
+}
+
+QImageViewer::~QImageViewer () {
+}
+
+bool QImageViewer::loadFile (const QString& file) {
+
+    QImageReader reader(file);
+
+    reader.setAutoTransform(true);
+
+    QImage image = reader.read();
+
+    if (image.isNull()) {
+        return false;
+    }
+
+    setImage(image);
+
+    return true;
+}
+
+bool QImageViewer::saveFile (const QString& file) {
+
+    if (file.isEmpty() == true) {
+        return false;
+    }
+
+    QImageWriter writer(file);
+
+    bool f = writer.write(_image);
+
+    if (f == false) {
+        qDebug() << writer.errorString();
+    }
+
+    return f;
+}
+
+bool QImageViewer::saveFileDialog (const QString& file) {
+
+    QString fileName = QFileDialog::getSaveFileName(this, tr("Save Image File"), file, tr("Image Files (*.png *.jpg *.bmp)"), nullptr, QFileDialog::DontUseNativeDialog);
+
+    return saveFile(fileName);
+}
+
+void QImageViewer::setImage (const QImage& image) {
+
+    //qDebug() << image;
+
+    _image      = image.copy();
+    _zoomFactor = 1.0;
+
+    _imageLabel->setPixmap(QPixmap::fromImage(_image));
+
+    zoomReset();
+}
+
+const QImage& QImageViewer::image () const {
+
+    return _image;
+}
+
+void QImageViewer::setText (const QString& text) {
+
+    _imageLabel->setText(text);
+}
+
+double QImageViewer::zoomFactor () const {
+
+    return _zoomFactor;
+}
+
+void QImageViewer::zoom (double factor) {
+
+    _zoomFactor = factor;
+
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+    _imageLabel->resize(_zoomFactor * _imageLabel->pixmap(Qt::ReturnByValue).size());
+#else
+    _imageLabel->resize(_zoomFactor * _imageLabel->pixmap()->size());
+#endif
+}
+
+void QImageViewer::zoomIn () {
+
+    zoom(zoomFactor() * 1.25);
+}
+
+void QImageViewer::zoomOut () {
+
+    zoom(zoomFactor() * 0.8);
+}
+
+void QImageViewer::zoomReset () {
+
+    zoom(1.0);
+}
+
+void QImageViewer::print () {
+
+    QPrintDialog dialog(&_printer, this);
+
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+    if (dialog.exec()) {
+        QPainter painter(&_printer);
+        QRect rect = painter.viewport();
+        QSize size = _imageLabel->pixmap(Qt::ReturnByValue).size();
+        size.scale(rect.size(), Qt::KeepAspectRatio);
+        painter.setViewport(rect.x(), rect.y(), size.width(), size.height());
+        painter.setWindow(_imageLabel->pixmap(Qt::ReturnByValue).rect());
+        painter.drawPixmap(0, 0, _imageLabel->pixmap(Qt::ReturnByValue));
+    }
+#else
+    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 QImageViewer::keyPressEvent (QKeyEvent* event) {
+
+    //qDebug() << "Key =" << event->key();
+
+    switch (event->key()) {
+        case Qt::Key_Escape:
+            zoomReset();
+            break;
+        case Qt::Key_Plus:
+            zoomIn();
+            break;
+        case Qt::Key_Minus:
+            zoomOut();
+            break;
+        default:
+            QWidget::keyPressEvent(event);
+            break;
+    }
+}
+
+void QImageViewer::enterEvent (QEvent* event) {
+
+    Q_UNUSED(event);
+
+    setFocus();
+}
+
+void QImageViewer::leaveEvent (QEvent* event) {
+
+    Q_UNUSED(event);
+}
+

src/plugins/imageviewer/QImageViewer.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include <QtWidgets/QLabel>
+#include <QtWidgets/QWidget>
+#include <QtWidgets/QScrollArea>
+#include <QtGui/QImage>
+#include <QtGui/QKeyEvent>
+#include <QtPrintSupport/QPrinter>
+
+class QImageViewer : public QWidget {
+
+    Q_OBJECT
+
+    public:
+        explicit QImageViewer (QWidget* parent = 0);
+       ~QImageViewer ();
+
+        bool                    loadFile                (const QString& file);
+        bool                    saveFile                (const QString& file);
+        bool                    saveFileDialog          (const QString& file);
+        void                    setImage                (const QImage& image);
+        const QImage&           image                   () const;
+        void                    setText                 (const QString& text);
+
+        double                  zoomFactor              () const;
+
+    public slots:
+        void                    zoom                    (double factor);
+        void                    zoomIn                  ();
+        void                    zoomOut                 ();
+        void                    zoomReset               ();
+        void                    print                   ();
+
+    protected slots:
+        void                    keyPressEvent           (QKeyEvent* event);
+        void                    enterEvent              (QEvent*    event);
+        void                    leaveEvent              (QEvent*    event);
+
+    private:
+        QImage                  _image;
+        QScrollArea*            _scrollArea;
+        QLabel*                 _imageLabel;
+        double                  _zoomFactor;
+        QPrinter                _printer;
+};
+