Qt Don't resize window when scaled QPixmap exceeds bounds

I'm using a QPixmap to show an image inside a QLabel, and when the image is scaled up exceeding the bounds of the parent widgets layout it's currently in, the window resizes to fit it again, then I also can't make the window smaller and scale down the image. Is there a specific QSizePolicy I need to put on the parent main windows layout, or the label itself, or some other set function?

Or is a solution that instead of scaling the image content up so it eventually exceeds the label bounds, I need to be cropping in the image at a certain point so it's never outside of the label?

w_content = new Content;

QStackedLayout *s_layout = new QStackedLayout(contentContainer);
s_layout->setStackingMode(QStackedLayout::StackAll);
s_layout->setSpacing(0);
s_layout->setContentsMargins(0, 0, 0, 0);
s_layout->addWidget(w_content);

Content::Content(QWidget *parent) : QWidget(parent), contentLabel(new QLabel) {
    QVBoxLayout *c_layout = new QVBoxLayout(this);

    contentLabel->setBackgroundRole(QPalette::Base);
    contentLabel->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);
    contentLabel->setAlignment(Qt::AlignHCenter | Qt::AlignVCenter);
    contentLabel->setScaledContents(false);

    contentImage = new QImage("C:\\Users\\user\\Downloads\\test.png");
    contentPixmap = QPixmap::fromImage(*contentImage);
    contentLabel->setPixmap(contentPixmap);

    c_layout->setSpacing(0);
    c_layout->setContentsMargins(0, 0, 0, 0);
    c_layout->addWidget(contentLabel);
    this->setLayout(c_layout);
}

void Content::scaleImage(double factor) {
    m_scaleFactor *= factor;
    w = contentPixmap.width()*m_scaleFactor;
    h = contentPixmap.height()*m_scaleFactor;
    QPixmap pm = contentPixmap.scaled(w, h, Qt::KeepAspectRatio, Qt::FastTransformation);
    contentLabel->setPixmap(pm);
}