Re: DHGR Correction for KEGS32 & AppleWin

["Bryan Parkoff" <none@nospam.net>]

"Andy McFadden" <fadden@fadden.com> wrote in message 
news:4468c271$0$65492$742ec2ed@news.sonic.net...
> mdj <mdj.mdj@gmail.com> wrote:
>> If the emulators appear to be mapping the colours incorrectly, I'd
>> venture that it's because the emulators choose to more closely mimic
>> the composite video signals produced by all Apple II's. Remember, the
>> IIGS's RGB output is only an approximation of the quasi-NTSC signal
>> produced by the composite video out. You are probably correct that the
>> IIGS approximation is 'wrong', it is after all only 4 bits of
>> resolution per colour channel.
>
> I did an experiment once with a Magnavox monitor attached to my IIgs.  I
> don't recall the monitor's model number, but it was the kind that
> A2-Central used to sell.  The nifty thing about it is that it would select
> from multiple inputs with switches on the back.
>
> So, I connected both the RGB and composite outputs from the IIgs to the
> monitor, cranked up Dazzle Draw, and flipped back and forth between the
> two inputs.
>
> As you might expect, there were significant differences between the two.
> Not just in color, but in how the pixels blur together.
>
> My goal was to accurately reproduce the IIgs RGB output in DHGR for the
> CiderPress conversion, but I found a lot of combinations that didn't make
> sense -- every pixel depends on the current color and the previous color,
> but sometimes it's more dependent than others.  Rather than try to 
> reverse-
> engineer the signal that was being emulated/generated/mangled, I punted
> on it and implemented something close.  (Actually, I implemented 4 
> different
> modes: one that works the way the //e tech note describes, one that looks
> like the IIgs display, one that does an ideal 140x280 screen, and one B&W.
> The colors I just mapped to the usual IIgs values.)
>
> I also didn't implement the weird standard hi-res stuff that gets you
> browns and yellows.  I don't think most emulators to that either.
>
> -- 
> Send mail to fadden@fadden.com (Andy McFadden) - http://www.fadden.com/
> CD-Recordable FAQ - http://www.cdrfaq.org/
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Andy,

    I agree.  I am sure that you will depend on me for the new 
implementation of DHGR from my future source code for your CiderPress 
project.  If you want cut-off in HGR to produce one of 16 colors such as 
yellow, brown, dark blue, etc.  It is how LGR and HGR use DHGR table which 
it looks real in Apple IIgs' RGB as emulated NTSC.
    In my project, it allows people to choose to use screen formats -- Apple 
//e's 80 Col / RGB card, Apple IIgs' RGB, and true NTSC.  It is not the 
color format, but it is the pixel structure.  True NTSC is the future 
implementation, but it will not look great in SVGA screen.
    I concentrate Apple IIgs' RGB project to produce DHGR this year.

Bryan Parkoff