title: Masking out the upper or lower 4 bits results in the same image
body: <p>I am processing a 12-bit image which is unfortunately store as a 16-bit tiff. However, I do not know which 4 of the 16 bits are useless. So I tried three methods: mask each pixel with 0xFFF0, 0x0FFF, or 0x0FF0. It appears to me the resulting image of these three methods look just the same, but their md5 values are different. Why does this happen? Are there any differences if I use any of these three images for other purposes later?</p>