iregular shaped LED strip screen

[Dahlberg77]

Hello everyone, I am trying to build an LED screen shaped as a guitar. I want it to be able to display graphics as if it was a square screen.I am using WS2812 strip and a Teensy 3.1.Is there a way to map out each pixel (see picture). For example. from top left pixel nr. 5 is actually the first pixel, and pixel nr.26 is actually pixel nr. 3. would it be possible to map ot each pixel as pixel nr.1 = x5y1 and pixel nr.26 = x3y2. I am not that good at programming, so how would that look in a sketch??

Best regards
Colin Dahlberg