#define horiz_width 15
#define horiz_height 15
-static char horiz_bits[] = {
+static unsigned char horiz_bits[] = {
0x00, 0x00, 0x00, 0x00, 0xff, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0xff, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0xff, 0x7f, 0x00, 0x00, 0x00, 0x00};