UV proportional scaling

Hi
How to scale proportionally to UV from the center to the edge?

Normal UV:
http://clip2net.com/s/3FkBtzA

Scaling proportional UV:
http://clip2net.com/s/3FkBwFcThanks

Enable proportional editing and set falloff


Select the centre vertex and scale with the proportional size big enough to cover all the points


Thanks very much!