如何调整qt中加载图像的大小

Question

我尝试加载图片，但加载的图片非常小。我其实不太了解QLabel的用法。有人可以帮我弄清楚如何调整加载图像的大小吗？

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);

     resize(500, 400);
 }

 void ImageViewer::loadFile(const QString &fileName)
 {
     if (!fileName.isEmpty()) {
         image = new QImage(fileName);
         if (image->isNull()) {
             QMessageBox::information(this, tr("Image Viewer"),
                                      tr("Cannot load %1.").arg(fileName));
             return;
         }
         imageLabel->setPixmap(QPixmap::fromImage(*image));
         scaleFactor = 1;
         updateActions();
     }
 }