
Tutorial to create a new image for menu:

1) First find an image.
2) With Gimp, open image and check there is a alpha channel. If not add one.
3) Convert image into back and white (Menu Image - Mode - Grey levels).
4) Use the degrade tool with option (Menu Tools - Paint - Degrade - CTRL+L):
* Mode: Erase color (you can also try "Elear only") 
* Opacity: 50 +/-
* Offset: 0
* Shape: Linear
* Select on image top of file and drag to bottom.
Il est possible aussi d'augmenter la transparence globale depuis le calque.
