I have developed a Qt application which can render 3D files.
One of its features is an option to take screenshots of the current state of the 3D rendering.

Here is the code snippet,

// Set capture entity
view->setCaptureEntity(sceneRoot);

// Save the rendering by calling this method
void My3DQtViewer::saveImage(QString filename)
{
    m_screenshotfilename = filename;
    m_renderCaptureReply = m_renderCapture->requestCapture();
    connect(m_renderCaptureReply, SIGNAL(completed()), this, SLOT(saveImageToFile()));
}

// Save image to file
void My3DQtViewer::saveImageToFile()
{
    m_renderCaptureReply->saveImage(m_screenshotfilename);
}

The code works fine and I am able to take screenshots perfectly.
Is there any way I can control the resolution/quality of the image being saved?

If I can present the user with options to change the resolution of the output image, how will I incorporate this in the code?

Thanks