[Coco] Compressed pictures

coco at yourdvd.net coco at yourdvd.net
Sun Apr 29 01:32:19 EDT 2007

Hello Arthur: I have wondered recently if there existed archives of the
Delphi and CompuServe CoCo SIG's from back in the day. Are they online
somewhere (perhaps at delphi or compuserve themselves? I suppose I
could do some searching)... Thanks - Robert
P.S. I remember the program of which you speak, the one you wrote. I
think it was the one I used to transmit graphics screens as ascii
rather than binary many moons ago.. r

> -------- Original Message --------
> Subject: Re: [Coco] Compressed pictures
> From: Arthur Flexser <flexser at fiu.edu>
> Date: Sat, April 28, 2007 4:05 pm
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> It is unclear why you would find LOADMing a 6K screen "too much";  it
> shouldn't
> take much time to load, and the fact that it is 3 times longer than
> the main
> program seems to me not particularly relevant.  If you want to
> compress the
> picture, a decent algorithm is to use byte, rather than bit,
> repetitions and
> think of the screen as a series of 8-bit wide byte columns.  The same
> byte
> repeats very frequently in vertically adjacent positions in a typical
> graphics
> screen.  A program I co-wrote years ago, MAXCMP.BAS, uses this and may
> be online
> somewhere in a CoCo archive. (That one took the additional step of
> converting
> the resulting screen to printable ASCII bytes and embedding the resulting
> encoding into a generated BASIC program that when run displayed the
> picture.  
> It was listed and written up in some issue of Rainbow, in one of Marty
> Goodman's
> columns.  It should also be in the Delphi archives, along with a detailed
> description of its compression algorithm.)
> Art
> On Sat, 28 Apr 2007, Diego wrote:
> > While writing some of my BASIC programs, I thought about adding a intro
> > screen. The options were add the drawing commands to the program (slow,
> > limited) or load a graphic screen. But even a PMODE 3 screen is 6Kb,
> a bit
> > to much for a 2 Kb program So I came up with a very simple compression
> > rutine. 2 bit for color, 6 bits for how many pixels of that color. Some
> > sample simple screens came down to just under 1 Kb (I know that some
> complex
> > screens can become a lot larger than the original) My question: Is
> there
> > some format/way to get a screen picture+loader in less than 2 Kb thatls
> > already out there somewhere?
> > 
> > Diego
> > 
> > 
> > -- Coco mailing list Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
> > 
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