Why do people always suggest finding the digest to compare two files? Graciously assuming calculating the digest is instantaneous, using the digest method requires reading the entire file whereas one can usually exit after one pair of reads using a byte for byte comparison.

Using the digest method is great when comparing a file against multiple others over a long time period. It's a poor method when comparing two files.

If they match chances are they are the same image.

If you're going to follow up by checking the files byte for byte, it might make more sense to find the digest of the first X bytes of the file instead of the digest of the entire file.