[PLUG] converting scanned line art to a limited color set

[Michael Rasmussen]

Galen Seitz wrote:
> Piet van Weel <pmvw at wbcable.net> wrote:
> > I would probably dump the image into GIMP and drop the color base down
> > from 16 bajillion colors and reduce it down to 256 or 16 colors. That
> > will definately reduce the size of the file.
> 
> I was sort of hoping to avoid GIMP, primarily because I have limited
> experience with it.  If this is easy do with GIMP, I'll explore that
> option.

This question got me curious.  So I tried it with the Slug Velo host
patch image, you can see th original at http://www.slugvelo.org/ I'm
referring to the green patch image.

The full sized, full color PNG file is 1.2MB.

Loaded image into Gimp.
Right Click, File, Save As, renamed to color_test1.gif
  (Gimp will auto convert based on filename)
Said OK to exporting and converting to indexed
Accepted all defaults

New file  is 393K

Now for real optimization

CTRL-A to Select All
Right Click, Image, Mode, Indexed
Accepted "Generate Optimized Palette" option, changed the number of
colors to 4.
Right Click File Save As color_test2.gif

New file is  56K

This seems to be easy enough (I had to do it to see how to do it) and
the fiel size trimming, 1.2MB to 56K, would seem to be the kind of thing
you're looking for.

Repeated the indexing option, this time changing the number of colors to
3.  

New file is 48K

You can see the files I"ve just described and a restatment of the
process at http://www.patch.com/colordepth/

-- 
    Michael Rasmussen, Portland Oregon  
  Be appropriate && Follow your curiosity
        http://www.patch.com/words/
  The fortune cookie says:
<hop> when you start making only stupid mistakes that are obvious, thats
      when you start getting competent
<hop> because you don't make fundamental misunderstanding mistakes
<hop> and thats a *good* sign.