#define rook_width 32
#define rook_height 32
-static char rook_bits[] = {
+static unsigned char rook_bits[] = {
0x00,0x00,0x00,0x00,0x00,0xc0,0x01,0x00,0x00,0x30,0x06,0x00,0x00,0x0c,0x18,
0x00,0x00,0x03,0x60,0x00,0xc0,0x00,0x80,0x01,0x20,0x00,0x00,0x02,0x20,0xfc,
0x2f,0x06,0x20,0xc0,0x1c,0x06,0x20,0xdc,0x0c,0x06,0x10,0xd8,0x38,0x04,0x10,