Huge response time while changing slides on the Pi

[rednaks]

If you are using a raspberryPi, you will notice a big delay between pushing the button to the next slide and the response from the Pi.
I expect that the render operation cost alot and we have to change that.
Maybe we have to render at least 3 pages: the current, the next and the previous.

[rednaks]

After some tests, I figured out that the render time on the Pi is 0.568 and it's alot ! (Don't forget the networks issues also ...)