[Coco] Any info on a mystery 256 color GIME mode?

[Roger Taylor]

At 09:07 AM 12/3/2003 -0500, you wrote:
>Nickolas Marentes wrote:
> >I was just wondering what your opinions are on my personal quest to
> >resolve the secret 256 color mode...is it real or is it fake?
>
>I am sure I read or saw an article on the GIME and the 256 color mode at
>some point, but can't remember the magazine.  Anyone else remember seeing
>this informaton mentioned and if so, do you remember what magazine it was
>in?
>
>I tried going through my stacks of old magazines and so far, all I ran
>across was an article in August '83 Hot CoCo claiming you can get 1000s of
>color hues on a CoCo.  The author says he combines three techniques:
>"First, buff-on-black in PMODE 4 always generates additional colors. . . .
>Second, in the other graphics modes colors placed close to each other
>sometimes generate a third color--again often depending on the degree of
>the slant. . . .  The third concept deals with mixing modes. . . .  You do
>this by superimposing one mode over another or 'fooling' the computer.
>The standard syntax for a graphics mode is this:  PMODE 4,1:PCLS:SCREEN
>1,1  To superimpose another mode, you need one more instruction, PMODE
>3,1.  Do not add SCREEN 1,1."  The article also says "Radio Shack does not
>tell you that you can mix these modes".


It's almost exactly like the term "subclassing" in a "windows" or 
procedure-based application, where you initiate a control or window, then 
change it's message entry point to your own routine, and intercept the 
messages, then pass things you don't handle back to the original 
procedure.  Ok, maybe it's not quite the same.... but both are still a 
trick that the system doesn't know about.

You can also split an image into two side-by-side near clones by changing 
from PMODE 1/2 to PMODE 3/4.  Correct me if I'm wrong, but even logic will 
tell you that since the PMODE 1 and 2 modes take up 1/2 the scanline memory 
of PMODES 3 and 4, switching to x2 mode will cause 2 of the old scanlines 
to be displayed per line in the new higher-res mode.  There *really* isn't 
a good use for this, but it's neat to watch.  Likewise, you can skew an 
image into "slices" by drawing in PMODE 4 mode then switching to PMODE 2 
mode without clearing the screen.  I hope I'm right on this.  It's been 
ages since I've played around with the PMODE command.  Oh what fun it used 
to be as a teen.

My Projector-3 viewer is chock full of tricks similar to these, where I 
plot colors using one mode, and display the screen using another mode.  And 
to make you more dizzy, combine multiple types of dithering with optional 
screen flickering, and you get a big mess.  :)