support for rgb565 pls #620
Description
In embedded system, rgb565 is more common format than other.
bit order
R will be the most significant 5 bits: R = bits[15 ~ 11] G = bits[10 ~ 5] B = bits[4 ~ 0]
byte order
little endian: bits[7 ~0] first byte, bits[15 ~ 8] second byte
big endian: swap little endian bytes