Detect scroll speed gallery

I am making an app with gallery view and I have this problem. I have implemented resizing the image, to be bigger when it is centred when selected or the user stopped scrolling. But I want to do this: when doing a slow scroll, the image transitions slowly from its orig开发者_如何学Pythoninal size into the I defined. Kind of like htc music, when you are doing a slow scroll of the tracks and their images transition. If someone has any suggestions how I can detect the speed of scrolling and should I override an Gallery method maybe? I would appreciate any suggestions or thoughts.