#include <QApplication>
#include <QFileDialog>
#include <QString>
#include <QByteArray>
#include <QStringList>
#include <QImageReader>
#include <QMessageBox>
#include <QPixmap>

using namespace Qt::Literals::StringLiterals;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    
    QStringList mimeTypeFilters;
    const QByteArrayList supportedMimeTypes{ QImageReader::supportedMimeTypes() };
    for (const QByteArray &mimeTypeName : supportedMimeTypes)
        mimeTypeFilters.append(mimeTypeName);

    mimeTypeFilters.sort();

    QFileDialog fdlg;
    QImageReader imgReader;
    
    fdlg.setWindowTitle(u"Open a picture..."_s);
    fdlg.setDirectory(u"."_s);
    fdlg.setMimeTypeFilters(mimeTypeFilters);
    fdlg.setFileMode(QFileDialog::ExistingFile);
    fdlg.exec();
    
    imgReader.setFileName(fdlg.selectedFiles()[0]);
    imgReader.setAutoTransform(true);

    if (imgReader.canRead()) {
        QPixmap pixmap{ QPixmap::fromImageReader(&imgReader) };    // If this is added, the result will be incorrect.
        QMessageBox::information(nullptr, u"..."_s, 
                                 u"Width: "_s + QString::number(imgReader.size().width()) + u", Height: "_s + QString::number(imgReader.size().height()),
                                 QMessageBox::Close);
    }
                                     
    return a.exec();
}