Thx for your reply, i'm going to investigate a bit more like you said.
I gave that up in the first place, because sending 1 to line 0 and sending 1 to line 1 gave a strange result. Line 0 and 1 didn't match, they looked completely different.
Thx for the hint about sending 32 if I need a zero. I had that same problem too, that's why my arrow also has pixels on the line 0, 6 and 7