let image_int8 (a:int8) =
let (a1,a2,a3,a4,a5,a6,a7,a8) = a in
"(" ^ (string_of_int a1) ^ "," ^
(string_of_int a2) ^ "," ^
(string_of_int a3) ^ "," ^
(string_of_int a4) ^ "," ^
(string_of_int a5) ^ "," ^
(string_of_int a6) ^ "," ^
(string_of_int a7) ^ "," ^
(string_of_int a8) ^ ")"