title: QT - Select section of image
body: <p>I'm using QLabel and QPixmap to show image in my program. I would like to use something like snipping tool in Windows to let user to select part of image that will be processed further. </p>
  
  <p>For example, I load image, user select part of it (rectangle), and it shows it is selected and I can read coordinates that are selected, so I can proceed with processing only part of image.</p>