#
# 5799-WZQ (C) COPYRIGHT IBM CORPORATION 1986
# LICENSED MATERIALS - PROPERTY OF IBM
# REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
#
#$Header:README 12.0$
#$ACIS:README 12.0$
#$Source: /ibm/acis/usr/src/ibm/bitprt_ca/RCS/README,v $

This directory contains two utilities, used for communication
with the IBM 3812 Pageprinter, which are not documented elsewhere:
	sqzpmp
	usqzpmp_font
Both are invoked by the /usr/ibm/bitprt shell.

Use of sqzpmp ("squeeze a file and put it into pmp format"):
----------------------------------------------------------
A bitmap image being sent to the 3812 can be quite large,
and transmission time, even at 19.2KB, noticeably long. 
Sqzpmp reads a bitmap image file (see dumpaed(1)) from
the standard input, encodes it to reduce the file size, 
adds appropriate escape control sequences,
and writes it to the standard output for printing
on an IBM 3812 Pageprinter.

Data compression encoding is accomplished by the use of pre-defined
pmp macro sequences whereby single ASCII characters represent
specific bit patterns. (See ibm3812pp(8)). Said differently,
sqzpmp performs run-length encoding on the bitstream which 
defines the image.

Sqzpmp should remain important to the bitprt system, even with 
performance enhancements.

Use of usqzpmp_font:
-------------------
This file of pmp commands and macro definitions defines a font
used to decode the output of sqzpmp. At the present time, 
the bitprt shell merely places this file before the compressed
image in the data stream going to the 3812. While this technique
can double the size of the data stream, the results are 
noticeably better than not using compression at all. (However,
this directory does not include a way of passing a bitmap image
to the 3812 without compression.)

In the future, the usqzpmp_font ("unsqueeze-pmp font") will be
stored on the host machine serving the respective printer, at which
time it will no longer need to precede the image file. Sqzpmp will
then need to be modified to request use of the font.
