#define gray_width 16
#define gray_height 16
static unsigned short gray_bits[] = {
   0x6d6d, 0xd6d6, 0xbbbb, 0x6d6d,
   0xbbbb, 0xd6d6, 0x6d6d, 0xbbbb,
   0x6d6d, 0xd6d6, 0xbbbb, 0x6d6d,
   0xbbbb, 0xd6d6, 0x6d6d, 0xbbbb};