[Coco] Compressed pictures

[coco at yourdvd.net]

It was Special Interest Group IIRC. Do you remember the hack to the
Vidtex cartridge that allowed us to actually begin saving files? This
was before we had any serious Telecommunications Sofwtare - ah - those
were the days.. Now that you mention it, I don't know if SIG was used
anywhere else either - I had always assumed it was a universal term. -
robert

> -------- Original Message --------
> Subject: Re: [Coco] Compressed pictures
> From: Arthur Flexser <flexser at fiu.edu>
> Date: Sat, April 28, 2007 10:59 pm
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> 
> I'm not sure about the Delphi and Compuserve archives.  I recall
> somebody on
> this list archived the Delphi CoCo SIG MESSAGE base on a CD, but I'm
> not sure
> about whether anybody has archives of the data libraries.  Come to
> think of it,
> what does SIG stand for, again?  <something or other> Interest Group,
> I think.  
> A term I haven't heard in a long time.  Special Interest Group?  Subject
> Interest Group?  Was this term used in places other than Delphi and
> Compuserve?
> 
> MAXCMP.BAS was descended from the earlier PIXCMP.BAS, and added the
> capability
> of compressing double-screen CoCo Max pictures as well as PMODE 3 single
> screens, allowing scrolling of the double-screen ones by the arrow
> keys.  The
> point of having the graphics converted to printable ascii characters
> was to
> allow the transmission of graphics as text files, in the days before CoCo
> terminal programs were routinely capable of transmitting binary files,
> and when
> BBSes often restricted uploads to text files.  This "asciifying" step
> increased
> the size of the compressed graphics by a factor of 8/6 (1.33), since
> only the
> lower 6 bits of each ascii character could be used for representing the
> graphics.  The Compuserve and Delphi program data libraries had a
> large number
> of graphics files encoded using PIXCMP and MAXCMP.
> 
> Art
> 
> On Sat, 28 Apr 2007 coco at yourdvd.net wrote:
> 
> > 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
> > > > 
> > > 
> > > 
> > > --
> > > Coco mailing list
> > > Coco at maltedmedia.com
> > > http://five.pairlist.net/mailman/listinfo/coco
> > 
> > 
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
> > 
> 
> 
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco