fit in

void QSingleImageView::bestFit()
{
    Q_D(QSingleImageView);

    QSize imageSize = d->image.size();
    QSize size = viewport()->size();

    int w = imageSize.width(), mw = size.width();
    int h = imageSize.height(), mh = size.height();

    double rw = 1.0*mw/w, rh = 1.0*mh/h, factor = 1;

    if (rw < 1 && rh > 1)
        factor = rw;
    else if (rw > 1 && rh < 1)
        factor = rh;
    else if (rw < 1 && rh < 1)
        factor = qMin(rw, rh);
    else
        factor = qMin(rw, rh);

    d->setZoomFactor(factor);
}