% -*-LaTeX-*-
% Converted automatically from troff to LaTeX by tr2tex on Tue Dec 18 11:07:52 1990
% tr2tex was written by Kamal Al-Yahya at Stanford University
% (Kamal%Hanauma@SU-SCORE.ARPA)


\documentstyle[troffman]{article}
\begin{document}
%
% input file: idiff.1
%
\phead{IDIFF}{1}{25-Jun-90}

%.CM 3
\shead{NAME}
idiff, udiff -- convert byte stream to difference stream (b[n]-[bn-1])
\shead{SYNOPSIS}
\nofill
idiff $<$ original $>$ delta
udiff $<$ delta $>$ original
\fill
\shead{DESCRIPTION}
\par
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).
\par\vspace{1.0\baselineskip}
Use
{\it idiff}
to convert the original to a delta file, and
{\it udiff}
to restore.
\par\vspace{1.0\baselineskip}
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.
\shead{SEE ALSO}
fbm(1) for general discussion, pbm(1) for PBM routines.
\shead{BUGS}
None known.
\shead{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.
\begin{TPlist}{25-Jun-90  Michael Mauldin at Carnegie Mellon University}
\item[{25-Jun-90  Michael Mauldin at Carnegie Mellon University}]
Release 1.0 mlm@cs.cmu.edu
\item[{07-Mar-89  Michael L. Mauldin at Carnegie Mellon University}]
Beta release (version 0.9) mlm@cs.cmu.edu
\end{TPlist}
\end{document}
