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1990-03-09
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397 lines
Documentation for:
SHOWGIF 4.1B
by
Bill Parquet
and
Dave Sharpless
Copyright 1989-90
Introduction
How many times have you downloaded a GIF file from your
favorite BBS only to discover you wasted maybe 15 minutes and
50,000 bytes of download credits on an array of dots that doesn't
really deserve to be called a picture, or had a "bad code in
file" after the first 10 lines? Wouldn't it be nice to be able
to see the picture as you are getting it, and if you don't like
it, just abort the transfer, saving your time and ratios for
something more worthwhile? If so, SHOWGIF is just the program
for you! It is a TSR which sits in memory, quietly waiting for
the system to begin writing a GIF file. Once the write begins,
SHOWGIF switches to the appropriate EGA/VGA video mode, and shows
the picture as it is coming over. It is compatible with most
download protocols available.
System Requirements
SHOWGIF makes several requirements on your video hardware.
For SHOWGIF to function properly, your system must be equipped
with EGA or higher. SHOWGIF also requires about 64k of memory.
Operation Instructions
SHOWGIF should be installed sometime before you load your
terminal program. This installation can be performed simply by
typing "SHOWGIF" just before loading your terminal program, or
inserting "SHOWGIF" in the batch file for your terminal.
"SHOWGIF" will remain quiet in memory until a file with the
extension ".GIF" is created on your disk. "SHOWGIF" will go into
high resolution mode as soon as it gets enough information to
begin drawing. (usually after the second Ymodem block) From
that point, data will be put up on the screen just before it goes
to disk. If you want to abort this viewing process, press the
backspace key ("<-"). Note that this will abort the file
viewing process, and not the download itself. Aborting the
download (With ESC, ^C, ^X, or likewise) will also abort the
viewing, and bring up the "Incomplete picture" message.
Similarly, if the picture data is garbled, a "Bad code in
picture" will appear, aborting the viewing, but not the download
itself. Once you are done downloading and have left your
terminal program, type SHOWGIF /u (note the 'u' is lowercase).
This will remove SHOWGIF from your computer, returning all of
about 64k.
NOTE: Since SHOWGIF is activated on the creation of a GIF file
on your disk, COPYing a GIF file around will also kick in the
viewer.
Hints and Tips on the use of SHOWGIF
SHOWGIF can be put in your AUTOEXEC.BAT, but we don't
recommend it. If you have not done so already, create a batch
file which installs SHOWGIF, runs your favorite terminal program
and then uninstalls SHOWGIF. This method is better for two
reasons, one (1) because SHOWGIF is not constantly taking up
memory when it is not needed, and two (2) because you don't risk
installing something on top of SHOWGIF, which could lock up the
computer on SHOWGIF's removal.
Configuring SHOWGIF
If you have ever configured VPIC by Bob Montgomery, you
already know how to configure SHOWGIF. If not, then here is a
simple explaination. SHOWGIF (and VPIC) come with 10 or so
definition files which contain the name of your card, the amount
of memory, the plane switching strategy, and parameters for all
of the resolutions. Find the definition file which best matches
your card, and say CSHOWGIF <def-filename> -- For example
CSHOWGIF ORCHIDES.CFG. Typeing CSHOWGIF on its own will list the
current card name, resolution, and plane switching strategy.
These definition files can be modified if you want to
add/subtract resolutions
Which Protocols Work Best With ShowGIF?
It will take some experimentation to determine exactly which
protocols jive well with ShowGIF, but we can give you a few
suggestions on what to use and what not to use. Zmodem (DSZ) by
Omen Technologies has been found to work excellently with ShowGIF
at speeds up to 19200 baud. Qmodem 4.0/4.1 (-r- the Forbin
Project) internal protocols work all right, except at the very
beginning, where they will temporary activate SHOWGIF, the
deactivate, then restart. It sounds confusing, and looks fouled
up, but everything ends up working fine. Some protocols write to
disk before sending their ACK code will be hurt the most (as
ShowGIF dramatically increases drive access time) are not
recommended. Protocols such as SeaLink (CLINK 1.20) by System
Enhancement Associates which create a temporary file then rename
it are least recommended because they will never activate
ShowGIF. (The temporary file does not have the .GIF extension)
You should not notice any significant drop in CPS in protocols
which work well with ShowGIF. External modem users should not
notice any lengthy propagations between blocks (the RD light
staying off for more than second and half or more)
Update Information
1.0 α: First version of SHOWGIF <Not released>
1.0 ß: Several features added: <Not released>
* Status report at the end of viewing (Not a gif, bad code,
etc.)
* Support for ATI, separate versions of the program
* Switch back normal video if d/l is aborted before
viewer is aborted.
* Squeezing pictures to fit 320x200 (MCGA version)
2.0 : Several problems fixed: <Beta Test>
* Code parsing routine completely re-written for speed
* Rest of the main loop translated into machine language *
Lockup after "Picture is not a GIF" message resolved
* Picture information put up while drawing
* Stack frame is normalized after each picture -- no more
lockup's after viewing 'too many' pictures
* 500% overall increase in speed! (benchmark 20 seconds in
1.0 to 4 seconds in 2.0)
3.0 : Improvements made <Beta Test>
* Support for EGA
* X axis scaling for pictures larger than 320 MCGA,EGA
3.5 : Improvements made <First release>
* One program can handle various video cards
* Internal configuration for video hardware
* Support for 10 more video cards
3.7 : Improvements made <Beta Test>
* 16 color (EGA) modes supported in standard VGA
configuration (640x350 and 640x480)
* Offset picture difficulties corrected.
4.1 : Improvements made <Limited Second release>
* User definable resolutions (compatible with VPIC)
* Better judgement is used when choosing video modes.
4.1B : Addendum to second release <Second Release>
* Added two new plane switching modes TRIDENT,CHIPSN'TECH
* New Intro.
* Fixed a problem in VGA.CFG that slipped through in 4.1
(Oops)
* Made sure it puts the information at the bottom of that
screen
* Minor revisions to the documentation
Shareware notice
Like most authors of Shareware, we do not seriously believe
that you are going to send money. However, if you wish to make a
donation, it will be greatly appreciated. If you have any
comments, leave them to Bill Parquet on one of these fine boards,
us at The GIF Cache (419/531-2693) 9p-9a EST [invalid after MAY
1990!] or our favorite boards -- The Henrietta Outhouse (216/965-
5463), or N.O.I.S.E. BBS (419/473-8651 --FidoNet 234/17) Enjoy!
Specifications for the Config Files
If you have ever seen the video card configurations for
VPIC**, these should look fairly familiar. The top line of the
file is the name of the card being defined. You name the card
anything you wish. This particular parameter is just for future
identification. The line contains the plane switching
methodology*. If in doubt, just leave it alone. The next two
lines are not used by ShowGIF and are included just for
compatibility. The subsequent lines define all of the pertinent
video modes for your card. It consists of several numbers which
are defined as follows: 1) Mode type (0 for EGA, 1 for VGA -
this is related to the number of colors available) 2) Palette
definition (0 for EGA, 1 for VGA. VGA Palette definition is
considerably more precise. Use EGA palette definition only if
you are operating an EGA card!) 3-6) The values for AX,BX,CX,DX
required to switch the card into that particular mode (for
instance VGA 320x200 would be 0x13 0 0 0) 7) X resolution 8) Y
resolution 9) Number of colors available in this resolution.
*Not all of the plane switching techniques are supported. Those
cards which use CIRRUS will generate the Unidentified plane
switching technique warning and default to NONE. Either leave us
some mail on how to do it or stick with Plain Vanilla. (NONE,
TSENG, ATI, VIDEO7, PARADISE, EVEREX, TRIDENT, and CHIPSNTECH ARE
supported).
**VPIC is a first rate picture file viewer. 2.4 is the newest
version at the time of this writing. VPIC may
be obtained from
BOB MONTGOMERY
132 PARSONS RD
LONGWOOD FL 32779
for the price of about $15 for registration (I think).
Acknowledgments:
I'd like the following people for their contributions to ShowGIF:
Dave Sharpless - For originally coming up with the idea (...A
Zmodem that views .GIF's while downloading...), Writing the
original plane switching routines (pre-version 4.1B), the
intro, and convincing me to make this do EGA, support,
inspiration, and to take credit.
John Sharpless - For spreading this program around the country.
John Bridges - For releasing "VGAKIT.ZIP" from which the plane
switching routines in 4.1B on originated from.
360 x 480 mode:
I've seen several implementations of this bastard mode. As
far as I'm concerned, its a Super-VGA mode, i.e. only extended
VGA cards can do it. Besides, if you do own an extended vga
card, why not use 640x480? If you can find a really compelling
reason for us to put this in, let us know.
Thank you for using ShowGIF!
Send comments, complaints, complements, ideas, etc. to
BILL PARQUET
30231 BATES RD.
PERRYSBURG, OHIO 43551-3827