Check to see if the script mentioned below fits your needs. You’d have to be more specific, though. For one thing, 16 bit could be RGB 555 (1 bit ignored), RGB 565, RGBA 5551 or RGBA 4444. The script below does not implement RGBA4444, but it could.
Note that many graphics editors and image viewers do not properly import 16 bit subvariants that contain alpha.