[net.micro] CGA to Hercules Converter

tsmith@milano.UUCP (10/16/86)

A Chinese friend of mine has recently purchased a program
that draws Chinese Characters on a video screen.  The program
works great on machines equipped with a Color Graphics Card - but
unfortunately, He has a Mono Hercules board on his home PC.  Naturally,
the extensions to the program that allow a Herc board are mucho $$$'s
more, so he's looking for a less expensive solution.  What
he needs, I guess, is some sort of memory resident routine that will
trap graphic instructions to the CGA and convert them to the Herc
format.  Do any gentle net-landers have experience and/or code to
perform this feat?  Kindly E-Mail any information you may have....

Thanx
TJ

-- 
Thomas J. Smith @ MCC Software Technology
tsmith@mcc.com  
sally!im4u!milano!tsmith

asf@sbcs.UUCP (Alan S. Fink) (10/18/86)

> A Chinese friend of mine has recently purchased a program
> that draws Chinese Characters on a video screen.  The program
> works great on machines equipped with a Color Graphics Card - but
> unfortunately, He has a Mono Hercules board on his home PC.  Naturally,
> the extensions to the program that allow a Herc board are mucho $$$'s
> more, so he's looking for a less expensive solution.  What
> he needs, I guess, is some sort of memory resident routine that will
> trap graphic instructions to the CGA and convert them to the Herc
> format.  Do any gentle net-landers have experience and/or code to
> perform this feat?  Kindly E-Mail any information you may have....
> 
> Thanx
> TJ
> 
> -- 
> Thomas J. Smith @ MCC Software Technology
> tsmith@mcc.com  
> sally!im4u!milano!tsmith

Such a conversion program interests me too.  If such an animal exists can
someone perhaps post it to net.sources (assuming of course that its PD
software)?

Alan S. Fink
UUCP:  {allegra, hocsd, philabs, ogcvax}!sbcs!asf
ARPA:  asf%sunysb.csnet@csnet-relay.ARPA
CSNET: asf@sunysb.edu

               

berger@clio.Uiuc.ARPA (10/21/86)

If the program writes directly to screen memory, as many PC
specific programs do, he's out of luck.

dmt@mtunb.UUCP (Dave Tutelman) (11/06/86)

>> A Chinese friend of mine has recently purchased a program
>> that draws Chinese Characters on a video screen.  The program
>> works great on machines equipped with a Color Graphics Card - but
>> unfortunately, He has a Mono Hercules board on his home PC.  Naturally,
>> the extensions to the program that allow a Herc board are mucho $$$'s
>> more, so he's looking for a less expensive solution.  What
>> he needs, I guess, is some sort of memory resident routine that will
>> trap graphic instructions to the CGA and convert them to the Herc
>> format.  Do any gentle net-landers have experience and/or code to
>> perform this feat?  Kindly E-Mail any information you may have....

If the "graphic instructions to the CGA" are BIOS calls, then the
Hercules BIOS I posted to net.sources a few months ago will do the
trick.  (Sort of. The aspect ratio won't be quite right, and the image
won't use the whole screen, but it'll work.)

However, the unfortunate fact is that VERY few programs use BIOS calls
for graphic output.  Most write directly to display memory.  Since
there's no display memory trapping on most PC-compatible machines
(read here, "practically all"), you have no way of trapping the
graphics instruction.

What MIGHT BE feasible is a "daemon" that runs from time to time,
and "fixes" the screen by some transformation.  A few problems with
this are:
   -	Herc Board occupies different memory addresses from the CGA.
	Unless you have a memory board that maps into the CGA address
	space, you'll never capture the graphic writes.
   -	The algorithm would have to at least check (and maybe recompute)
	the whole screen, often enough to look like a reasonably smooth
	refresh.  I bet that'd be a brutal drag on real-time performance.
   -	I don't know which would give better (less objectionable?)
	images: using less than the full screen and an improper aspect
	ratio, using a two-pixels-to-three "dithering" algorithm,
	or using a one-pixel-to-two mapping and running off the edge
	of the Hercules screen.

Good luck, and if you find a solution please post it.

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