[Coco] The myth of the Coco3 256 color mode :)

Luis Antoniosi (CoCoDemus) retrocanada76 at gmail.com
Tue Apr 16 11:00:32 EDT 2013


Not only on CMP monitors but CMP CRT monitors. I tried once running the 256
colors demo on my LCD screen (using composite input) and it sucks.
Apparently all the fast switching screens don't work with lcd, at least my
LCD.


On Tue, Apr 16, 2013 at 10:55 AM, Robert Gault <robert.gault at att.net> wrote:

> There have been several recent threads about generating multi-color
> graphics screens on the Coco. One was for the Coco1 or 2, semigraphics was
> mentioned, and also the 256 color mode on the Coco3 prototype board. Also
> there is the flicker procedure where several different graphics screens are
> rapidly switched to yield a blended image.
>
> While all the above are of interest, there is one Coco3 mode which
> provides close to 256 colors at one time which may soon be lost to us
> forever. It works on composite monitors only (which are a dying breed) and
> is not supported by any emulator. The mode was discussed in a thread on
> coco3.com and that site has been problematic of late and is frequently
> off the air.
> http://www.coco3.com/**community/2009/02/256-color-**mode-composite-mode-*
> *artifacting/comment-page-1/#**comments<http://www.coco3.com/community/2009/02/256-color-mode-composite-mode-artifacting/comment-page-1/#comments>
> There are 7 pages of comments.
>
> I don't want to see this mode lost in time and mythology as happened with
> the supposed mode on the prototype board. :) So here is a short demo of the
> technique for a Coco3 and CMP monitor.
> 10 HSCREEN4:PALETTE0,0:PALETTE1,**16:PALETTE2,32:PALETTE3,48
> 20 M=&H60000:POKE&HFFD9,0
> 30 FOR Y=0TO3
> 40 FOR X=315 TO 331 STEP 4
> 50 FOR C=1TO3
> 60 HCOLORC,0:HLINE(X+20*(C-1)-Y,**71+10*Y)-(X+20*(C-1)-Y,80+10***Y),PSET
> 70 NEXTC,X,Y
> 80 GOTO80
>
> By rights, the above should give just vertical gray lines on a CMP
> monitor. Instead, you see four rows of three shaded colors, blue, purple,
> red-orange, and green. It is possible to create a pattern that appears to
> yield 256 colors, although depending on your CMP monitor some will seem
> duplicates.
>
> I've written a Basic-ML pair of programs that will load a .bmp image that
> displays perhaps 256 colors without any flickers associated with screen
> swaps. The following restrictions apply.
>
> * This works only on a TV/composite monitor. It will not work with an
> emulator or RGB monitor.
> * BMP images are limited to 256 colors. The width
> * must be 256 pixels or less.
> * With a 128K Coco3, the total image must be 65K bytes or less. With a
> * 512K Coco3, the total must be 458K bytes or less.
> * The screens used are 640x225x4.
>
> You need to use a PC graphics program to convert an image to the above
> conditions and place the image on a .dsk or real Coco disk. The program
> will work nicely with Drivewire.
> I can send a program disk on request but this list does not like
> "attachments".
>
> All of the above resulted from a discussion started by Potatohead (who are
> you?) and a Coco program called GrafExpress.
>
> Robert
>
> --
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> Coco at maltedmedia.com
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>



-- 
Long live the CoCo



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