        Installation instructions for HCOMPRESS on Unix machines
                    R. L. White, 20 April 1992

This directory contains a makefile for building HCOMPRESS on a Unix
machine and some C-shell scripts to make using the programs a little
easier.  This makefile has only been tested on Suns and DECStations, so
some small modifications may be required for other machines.

Steps for installation:

(1) Copy the contents the contents of this directory into the
    source directory.
(2) Do "make all" (or just "make") to compile and link the programs.
(3) Edit makefile: change the INSTALLDIR variable to point to the
    directory where you want the executables to reside.  By default
    they will go into ${HOME}/bin, i.e. your bin directory.  You should
    chose a directory that is included in your path.
(4) Do "make install" to install the programs in your chosen directory.
(5) Do "rehash" to update your hash tables.
(6) There is a man page in the file hcompress.1.  It can be installed
    in your man directory.  The doc directory includes both a plain text
    version of the man page (hcompress.txt) and a postscript version
    (hcompress.ps).

Now the programs should be ready to run.  You may want to customize
the shell scripts for your applications.  Some possible changes to
consider:

(1) There are shell scripts to compress multiple files in FITS format
    and in hhh/hhd format.  If you usually use some other formats you
    could include in the script a conversion from your format to
    one of the accepted formats.
(2) The amount of compression is determined by the scale factor, set by
    the -s option in the programs.  For astronomical images the compression
    is generally limited by the amount of noise in the images and the
    scale factor should be about 2 times the RMS noise in the image.
    For noiseless images any non-zero scale factor will give up some
    information, so the choice of scale factor will be determined by how
    much you are willing to lose.  A default scale factor of 666 is used
    in the scripts -- this should probably be changed to a value appropriate
    for your typical images.  If you like, you could set this default to 0
    (lossless compression.)

Copyright (c) 1993 Association of Universities for Research
in Astronomy. All rights reserved. Produced under National
Aeronautics and Space Administration Contract No. NAS5-26555.
