QWidget(parent),

ui(new Ui::ImageViewer)

{

ui->setupUi(this);

connect(ui->buttonOriginalSize, &QToolButton::clicked, this, [this]{ scaleImage(100); });

ui->labelView->addAction(ui->actionPrintImage);

{

ui->labelView->setPixmap(QPixmap::fromImage(image));

// If the image is larger than the viewport scale it to fit the viewport.

// If the image is smaller than the viewport show it in its original size.

if(image.size().width() > ui->labelView->size().width() || image.size().height() > ui->labelView->size().height())

ui->buttonFitToWindow->setChecked(true);

else

scaleImage(100);

{

QPrinter printer;

QPrintPreviewDialog dialog(&printer);

connect(&dialog, &QPrintPreviewDialog::paintRequested, &dialog, [&](QPrinter* previewPrinter) {

QPainter painter(previewPrinter);

QRect rect = painter.viewport();

#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)

QPixmap pixmap = *ui->labelView->pixmap();

#else

QPixmap pixmap = ui->labelView->pixmap(Qt::ReturnByValue);

#endif

QSize size = pixmap.size();

size.scale(rect.size(), Qt::KeepAspectRatio);

painter.setViewport(rect.x(), rect.y(), size.width(), size.height());

painter.setWindow(pixmap.rect());

painter.drawPixmap(0, 0, pixmap);

});

dialog.exec();

{

// Enable/disable the automatic resizing of the label inside the scrollbar

ui->scrollArea->setWidgetResizable(enabled);

// When disabling the fit to window scaling, revert back to the original image size

if(!enabled)

scaleImage(100);

{

// Make sure the slider is updated when this is called programmatically

ui->sliderScale->setValue(scale);

// Update our scale factor

qreal factor_change = (scale / 100.0) / m_scale_factor;

m_scale_factor = scale / 100.0;

// Resize the image

#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)

QPixmap pixmap = *ui->labelView->pixmap();

#else

QPixmap pixmap = ui->labelView->pixmap(Qt::ReturnByValue);

#endif

ui->labelView->resize(m_scale_factor * pixmap.size());

// Uncheck the fit to window button

ui->buttonFitToWindow->setChecked(false);

// Fix scroll bars to zoom into center of viewport instead of the upper left corner

const auto adjust_scrollbar = [](QScrollBar* scroll_bar, qreal factor) {

scroll_bar->setValue(static_cast<int>(factor * scroll_bar->value() + ((factor - 1) * scroll_bar->pageStep() / 2)));

};

adjust_scrollbar(ui->scrollArea->horizontalScrollBar(), factor_change);

adjust_scrollbar(ui->scrollArea->verticalScrollBar(), factor_change);