Re: Apple II Colour --> RGB

[spam@luddite.ca (Ned Ludd)]

Paul Schlyter <pausch@saaf.se> wrote:

> In article <20030922000434.16646.00001378@mb-m02.aol.com>,
> Michael J. Mahon <mjmahon@aol.com> wrote:
>  
> > ][GIF is trying to solve a very difficult problem, since it has such
> > a limited palette available on the Apple II, even in DHR.
>  
> Que?
>  
> The 256-color palette in GIF images is indeed limited compared to
> today's tandards.  But the Apple II had only 16 colors even in lo-res
> and text modes, and fewer still in hi-res mode.....

Well it turns out that ][ Gif is the only viewer I could find that will
actually open gif89a files. It even does animations (very slowly)...
curiously, all of the 16-bit gif viewers I tried wouldn't recognize any
of the GIFFs I threw at them.

Haven't had any luck with finding a gif palette that translates to DHR,
though I found that ][ Gif handles the colours fairly well in HiRes mode
(it alternates horizontal lines to "mix" colours), unfortunately this
approach allows a maximum practical resolution of 140x96 which is a bit
pathetic for photos.

On the plus side, I've found that b/w photos can translate very nicely.
I got pretty good results by first resizing greyscale images to 280x192
and then saving the gif file with the palette limited only to #ffffff
and #000000. Dithering is the key here, I found that generally either
pattern or diffusion were the best methods.
][ Gif converts the b/w gif very crisply, but saving as HiRes seems to
introduce pixel blurring in the mid-tones which smooths the transitions
somewhat.

Not sure why I started messing about with this in the first place, but
now I'm thinking of doing a HiRes slideshow of my summer vacation ;-)

Simon