#include <QCryptographicHash>
#include <QDebug>
#include <QGuiApplication>
#include <QPixmap>

QByteArray save(const QPixmap &pixmap) {
  qDebug() << "=== save ===";
  qDebug() << "Saving" << pixmap.size();

  QByteArray data;
  QDataStream dataStream{&data, QIODevice::WriteOnly};
  dataStream << pixmap;

  qDebug() << "Saved size:" << data.size();
  qDebug() << "Saved hash:" << QCryptographicHash::hash(data, QCryptographicHash::Md5).toHex();

  return data;
}

QPixmap restore(QByteArray data) {
  QDataStream dataStream{&data, QIODevice::ReadOnly};
  QPixmap pixmap;
  dataStream >> pixmap;

  qDebug() << "=== restored ===";
  qDebug() << "Image size:" << pixmap.size();

  return pixmap;
}

int main(int argc, char *argv[]) {
  QGuiApplication app{argc, argv};

  QString pixmapName{"test.png"};

  QPixmap pixmap{pixmapName};
  Q_ASSERT(!pixmap.isNull());

  auto data = save(pixmap);
  pixmap = restore(data);
  Q_ASSERT(!pixmap.isNull());

  data = save(pixmap);
  pixmap = restore(data);
  Q_ASSERT(!pixmap.isNull());
  return 0;
}