Power Programmierung/Power-Programmierung CD 2 (Tewi)(1994).iso/doc/bildform/rle/rle.txt

Text File | 1994-06-30 | 8KB | 128 lines

101 things to do with .RLE
(But did not know what .RLE was!)

 By Chrisdos CBIG Sig Sysop
    [76703,717]

(c) 1986 by Chrisdos. All rights reserved.


RLE - Run Lenght Encoding.
    A method of encoding HiResolution bit mapped images so as to make it
possible to up and download the image to different brands of computers.
    There are a number of computers that can decode .RLE images, and
programs for others are being developed. All that is required is that
the computer have a HiRes screen of at least 256 pixels wide by 192 down.
.RLE images are in black and white, so color is not important. This provides
for compatability on a wide range of machines.
    The largest use of .RLE images at this point in time seems to be
on Commodore 64s, then TRS80 Color Computers, and others. There was, untill
recently, no software avalible for most machines to produce an .RLE image, but
this too is quickly being rectified.
    I will cover some basics of .RLE here, refering to Commodore 64
programs mostly as that as the computer I use most. I am sure that other
computers will have programs that do the same things avalible.

    RLE and Compuserve
    ------------------
    .RLE was first used to produce the HiRes weather maps (GO AWX-4) and
later for the CB Users Pictres (GO CB-65) and FBI 10 Most Wanted list (GO TEN)
and other images. The first decoding programs were for off line viewing on
most computers, untill the various VIDTEX programs could be updated to
do the graphics.
    When viewed off line, the .RLE data was captured in a ram buffer and
saved to disk, to be processed later by a displayer program. This was a bit
round-a-bout to say the least. I believe VIDTEX for the COCO was the first to
be able to display the .RLE images. Then came CBterm/C64 for the Commodore 64.
(CBterm is avalible in DL2 of the CBIG SIG, GO CBIG) Then VIDTEX 4.2 also
for the Commodore. There are also display programs, both for sale and public
for just about all the other popular computers.
    All the original images were provided by Compuserve, as there were
really no other programs to produce the .RLE information, and as such, there
were no databases of .RLE files to get at, you had to READ the image, you
could not really get to the file to, say, download it. But as programs became
avalible to produce your own .RLE images, users began to upload them to Forum
databases, where that could either be READ or DOWNLOADED. One of the first
such programs for the C64 was HR2RLE. (Avalible in DL2 of CBIG.) With this
program, users could convert their own pictures and upload them to share with
others. Of course, a corrisponding RLE2HR program was provided to check the
.RLE file produced to see what the image would look like in this format.
Again, programs for other compters are avalible now, or soon will be.
    Now viewing the files is fairly eazy, but where do you get the original
pictures to convert?? Well, on the C64 there are 2 main formats used most
often for hires images, this is Doodle and Koala. Almost all Doodle Images
can be translated directly to .RLE format. Koala take a little more work,
as it is a multicolor image, and some of the color must be converted to
black and white to get a good image. (Programs to do all kinds of conversions
are avalible in DL2 of CBIG. Do a BRO /KEY KOALA or BRO /KEY DOODLE)
So if you had an image you drew, you can usally find a program that will
get it into .RLE format. Not to be left out, some people use video digitizers
to produce an image, and then convert that.
There are even programs that will take images drawn on other compters and
directly translate it into a file compatable with your computer, that you can
then translate into .RLE that is even more compatable with other compters.
(See COCO64 in DL2 CBIG) And if that were not enugh, programs are even being
created to convert all the old ASCII Line Printer Art files into High Resolution
screen images. (LPT2HR, et al.) When things are done right, a program also
will reverse what it has done so it can convert in the oppisite direction as
well. All this leads back to the .RLE file again, once an image is converted
to the .RLE file, it can be uploaded to a Forums database,  there it can
either be Downloaded, if you wish to work on it off line, or READ if your
terminal program will display the image directly.
    A .RLE image ir composed of a control character header, that tells the
terminal program what type of file follows (for there is also MEDIUM resoltion)
and then a string of ASCII characters, each one representing the number of
pixels to set or not. At the end is another control string to turn graphics
off on your computer.   .RLE is relitivily easy to decode, and there is
a primer on doing it on your compter in basic to be found in dl2 of CBIG. If
a display program does not already exsist for your machine, this is the place
to start in writing your own. More .RLE information can also be had by doing
a GO VIDTEX and reading the tech library there.
    So now that you have created or downloaded a .RLE file and have
displayed it, what good is it? Well most programs should allow you to dump the
image to a printer or disk. If you can dump to disk, it is usally in one
of 2 ways. You save the .RLE data itself, or you save the hiRes screen in
a usable format. On  a CoCo, the screen is saved in a BIN dump format most
often, that can be redisplayed easyly. On a C64, depending on the program
involved, images can be saved in Doodle or Koala format, and used by these
programs, or other utilities. Again, other program exsist for other machines,
are are at least in the works. (See the file CBTERM.TXT in dl2 of CBIG for
a full index to CBterm and RLE conversion programs for the C64 compter. Also
there are programs for other computers as well. If you know of a .RLE program
I dont have, pleae upload it there.)
An example of a .RLE save would be VIDTEX 4.2 for the C64, it does not save the
screen, but records the RLE data in its RAM buffer, and will save that to
disk. Then it can be reloaded into VIDTEX from disk, and redisplayed. An
overlay utility has been written for Vidtexx 4.2 that will allow direct
saving of the HiRes screen, and this is a more usefull item and you can
save in a format compatable with drawing programs. (VTXDD2 and VTXKO2)

    Now, printing the image is what its all about isn't it?
It's nice to view the image, but its better to print it for later display.
This assumes you have a printer of course, and it is capable of doing
HiRes graphics. Some terminal/display programs allow for direct online dumping
of the HiRes screen (CBterm/c64 for example) while others reqire you
to save the image to disk and print it with another program. Either way, there
are programs that will allow this on most machines.
(Or at least being worked on, Check with the SYSOP of your machines' Forum.)
The latest advent in printing, is for those users that do not have a printer
that can do HiRes graphics directly, and that is a program that will produce
an ASCII line printer file directly from a HiResolution screen. This file
can be printer on any printer then. So things have come full circle !

As I stated, programs are being develped to do new things with .RLE graphics
on most computers. As a byproduct, commnications and utility programs are also
being improved.  .RLE was made to be compatable with a wide variety of machines,
and the list is growing each day. There is now even a full blown Forum
devited to .RLE graphics (GO PICS) and DL3 of CBIG contains the largest
collection of .RLE images at this time. (over 75 and growning, contribtions
welcome!)
There is no end to .RLE graphics, what started at a means of showing off the
Weater Radar Maps has grown into a huge picture and program database!

    For more help with program for your brand of computer, contact the
SYSOP of your machine's Forum, or the .RLE Picture Support SIG, or Browse
DL2 of CBIG, you never know what you can find there.
 -Chrisdos