IDIFF
Section: User Commands (1)
Updated: 25-Jun-90
Index
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NAME
idiff, udiff - convert byte stream to difference stream (b[n]-[bn-1])
SYNOPSIS
idiff < original > delta
udiff < delta > original
DESCRIPTION
Used as a preprocessor for compression algorithms. Some images
(especially grayscale and RGB) compress better when the compression is
performed on the difference between adjacent bytes, rather than the
bytes themselves (savings up to 30% are common).
Use
idiff
to convert the original to a delta file, and
udiff
to restore.
There are no magic numbers or headers, so there is no good way to tell
whether a file has been "idiffed" by examining the contents.
SEE ALSO
fbm(1) for general discussion, pbm(1) for PBM routines.
BUGS
None known.
HISTORY
Copyright (C) 1989,1990 by Michael Mauldin. Permission is granted
to use this file in whole or in part for any purpose, educational,
recreational or commercial, provided that this copyright notice
is retained unchanged. This software is available to all free of
charge by anonymous FTP and in the UUNET archives.
- 25-Jun-90 Michael Mauldin at Carnegie Mellon University
-
Release 1.0 mlm@cs.cmu.edu
- 07-Mar-89 Michael L. Mauldin at Carnegie Mellon University
-
Beta release (version 0.9) mlm@cs.cmu.edu
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- SEE ALSO
-
- BUGS
-
- HISTORY
-
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