Re: Help needed: Emulation of AppleII Graphic modes

[jon@i-manila.com (Jon Co)]

I remember reading somewhere that the bits on the right edge in DHR
affects the display on the other side.  How it does it I am not sure
because I can't find that document anymore.  Looked at the //c
technical reference manual did not reveal anything although i was sure
thats where I first saw it.

also Is it possible to set DHR to monochrome mode with soft switches
so that it displays 560-dot monochrome display or do I have to turn
down the color knob physically?
Holger Picker <pickerh@uni-muenster.de> wrote in message news:<Pine.A41.4.44.0302151123300.86570-100000@zivunix.uni-muenster.de>...
> Hello,
> 
> thanks a lot for your replies.
> 
> On 14 Feb 2003, Lazarus I. Long wrote:
> > you have guessed correctly.  I actually use a 5 pixel window, since 4
> > pixels is not enough information in certain cases.  when looking at a
> > 5 pixel window, the one you're coloring is the center one.
> Hmm... I've used this kind of technique for my emulator, too, when writing
> the code for a "sharp" hi-res output. It's just that I looked at three
> hi-res (1/280) pixel instead. :-)
> 
> > and you assume that there are 2 extra pixels on each side, with value 0.
> This also corresponds to what Mr. Mahon wrote:
> "Generally, you would be safe to assume that the bits
> 'shifted in' before and after the ends of the line are 0 (black)."
> And, I have to agree, it really seems to be some kind of art "how one
> simulates this 'artifact' NTSC color on a PC display". :-)
> Having quoted that, well, forgive me, Mr. Long, but I've seen you posting on
> this matter several times now, and I have also visited your web site before
> where you compare the results of different algorithms.
> > happy to send you the code if you want it.
> Well, would you mind, if I send you a (perhaps a bit longer) email about the
> code?
> 
> > > a) What size do the hires pixel have (I assume 1/280 i.e. 2/560, not 1/560)
> > correct
> >
> > > b) What happens if there are two bytes, the first with highbit on, the second with highbit off, like 0000001-1 0000000-0?
> >
> > you will loose the 2nd 1/560 pixel.  it just "goes away"  IIRC and you
> > get lowrez color there
> >
> > :)
> Ah, I see. Thanks for that information. I've kept wondering about this kind of
> thing for quite a while.
> 
> Kind regards
> 
>   Holger