Skuller: In that case you can use a simple potentiometer with high performance serial with the pink/white wires. (I mean approx. 20 Ohms,10W) like the dashboard-dimmer of certain cars.
Coucouillu: What project? It is a very ugly smd panel (two very small panel on the top of each other). It just contains an irlms6802 small 5A fet, a driver transistor-pair (for 5V-12V drive, and a pic10f206 (very small and cheap) for the pwm. The PWM solution is from software. I can attach the program, if you want.
gp0 and gp1 are inputs, and have a slight pullup internally, you can pull them to the ground with a switch.
The most difficult method to find the location of 12V input on the backlight panel, because it varies with the manufacturer, but usually there is a coil BEFORE reaching the two fets or transistors, and one ending of that coil is the hot spot for us.
The photo was made by my wife's phone, and in spite of the unusable quality, I think the size of my masterpiece is visible.