Fluently resize a QGroupBox

Hi. I have a QGroupBox that I want to resize (make it smaller) after clicking a button. For example if initial size of QGroupBox was 200px, I want it to become 100px (hiding contents from 101px - 200px). Is there any easy way to make it?
In groupBox I have an image and a text below. After clicking a button I want only image to be visible. And I would love it of the animation was fluent :)

I think you mean fluid not fluent, and I think you want to use QPropertyAnimation on the geometry property.