2000.02.29 21:55 "Re: Tiff verification utility", by Louis H. Sharpe II

Does anyone know if there is a program, or publically available algorithm which will allow me to generate a checksum for tiff images?

Message digests (such as MD5) are superior to checksums since they change in response to byte swaps. There is some (nearly) public code at:

http://theory.lcs.mit.edu/~rivest/md5.c

We have run this on TIFF files and stored the results externally to the TIFF files.

If the community wanted a tag for this value, we would have to register a tag and define some rules for its use. What bytes would be included in the calculation? Image bytes only or the full file (except that's self-referential)? I guess it could be the whole file minus the n reserved bytes occupied by the fixed-length MD5 ASCII-encoded result string.

Lou
Picture Elements, Inc.