Thanks for your quick answer !
I explain you my problem. I try to get the RGB pixel properties of an image and his position XY. I've tried to do it with Processing but my serial connection between Processing and Arduino is very approximate (maybe a wrong delay and/or configuration between them).
That's why I'm wondering if we can do that directly on Arduino without serial communication.
I googled "getpixel" on Arduino but several posts was about "TFTLCD library" and SD library. It doesn't match with my project which is to load an image on a Rainbowduino + 8x8 RGB.
Thanks 