%OP%PS1
%OP%LM5
%OP%FO 
%CO:A,12,72%
%C%%H2%ZRLE Documentation
%C%by
%C%Norm Lehfeldt


%H1%What is an RLE Graphic?

An RLE Graphic is an image stored in a form that is compatible with any 
computer display that is dot-addressable and offers resolution of at 
least 256X192 pixels. There is no gray-scale -- pixels are either on or 
off. The storage format uses only ASCII characters with codes from 
32 (space) to 127 (del). This range of codes insures that no control 
codes are part of the file and so the file can be transferred from 
computer to computer with no unexpected results.

RLE encoding programs have been written for many popular computers, but 
until there is a drawing program for the Z88 -- a highly unlikely 
development -- an encoding program for it seems unnecessary.

ZRLE, though, is a servicable program for decoding, displaying and 
printing RLE graphics which have been created on other computers. BBS's 
and some commercial data bases can be sources of such images.

%H1%How do I use ZRLE?

Before you can use ZRLE, you must have Z007A, a BASIC patch that 
implements graphic displays and screen dumps on the Z88. Z007A can be 
downloaded (as can many other valuable files and programs) from Phil 
Wheeler's Z88 BBS in Torrance, CA -- (213) 370 2754.

Install the graphic facilities with the statement, CHAIN"Z007A". 
(Throughout this discussion I will omit the RAM specification from LOAD 
and CHAIN statements. Such specification must be included if the file 
or program is not in the default RAM or EPROM).


Once Z007A is installed, invoke ZRLE with the statement, CHAIN "Z216B". 
The rest is easy -- simply follow the prompts. 

You must, of course, have an RLE file or two in the Z88's memory before 
you can see a picture. 

%H1%Things to keep in mind while using ZRLE.

Since the Z88 graphic display is only 64 pixels high, the image is 
displayed in three sequential sections. Print them out and paste them 
together to see the whole image.

When asked for a file name to decode, you must include a RAM or EPROM 
specification if the named file is not on the default device.

The program makes no validity check on the files to insure that they 
are in fact RLE graphic files. If you enter the name of another type of
file, the results are unpredictable -- except that the program will 
ultimately crash!

A file name that does not match anything in memory will crash the 
program. Restart with "RUN."

If you do not have an Epson-compatible printer connected, avoid 
pressing "P" at the prompt.

%H1%How can this program be improved?

If you are smarter than I you can convert the main processing loop, 
lines 50 to 180, to machine language. We would all appreciate the 
speedup.

The printer driver in Z007A issues spurious line feeds which require 
cutting and pasting the printouts. This needs to be fixed.

The printer driver also produces vertically elongated images on 24-pin 
printers. I would like it if someone could fix this, too!

If you have questions or comments on this program, I will try to answer 
them. Leave me a message on the Z88 BBS or on CompuServe.

Enjoy the program.

Norm Lehfeldt, CompuServe ID# 72466,3273
San Francisco, CA
3/16/90
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