[Coco] More colors on CoCo 1?

[Richard Atkinson]

Hi Joel,

It's possible to do exactly as you suggest. The multiple mode idea is
especially interesting, for example you could take a high resolution RG6
black and white picture and colour it in using an SG24 picture.

One problem you would notice would be a 30Hz flicker (25Hz on PAL). As a way
of getting round this, you could restrict the colours in the 2 pictures, for
example 2 SG24 pictures, by only allowing colours to alternate between 2
colours of the same brightness. The CoCo 1 has 4 brightness levels and 12
colours altogether, the colours at each brightness level being:

Level 0
Black
Dark Green (RG6 'black' or alphanumeric character 32, CSS=0)
Dark Orange (alphanumeric character 32, CSS=1)

Level 1
Blue
Red

Level 2
Green
Cyan
Magenta
Orange

Level 3
Buff
Yellow
Light Orange (alphanumeric character 96, CSS=1)

Although your choice of extra colours is limited to 13 extra ones in this
case, the flickering should be much reduced. If you're prepared to tolerate
a little more flickering, you could allow colour combinations between
colours having adjacent brightness levels, e.g. 0/1, 1/2, 2/3.

Richard


On 1/21/07, Joel Ewy <jcewy at swbell.net> wrote:
>
> Ok, this may be just wild speculation.  But couldn't one write a program
> that would flip between 2 9-color SG-24 screens to make a 64x192
> high(er)-color display on a CoCo 1 or 2?  Not that I'm seriously
> thinking of attempting such a thing.  It would take up 12K of RAM, but
> that in itself shouldn't be a show stopper on a 64K machine.  Resolution
> would be quite low, and the elongated pixels would be weird.  But I
> wonder if you could almost get a recognizable image by time-domain
> dithering the colors.
>
> Another question is whether the screens would even have to be in the
> same graphics mode.  Could one superimpose a 256x192 2-color bitmap over
> an SG-24 colorizer?  Or two?  That would require 18K.  Why would this
> not work?
>
> JCE
>
>
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