On 2007-12-28 00:11 +1000, Anthony Thyssen wrote:
> Andre Majorel on  wrote...
> > On 2007-12-24 13:01 +1000, Anthony Thyssen wrote:
> > > Andre Majorel on  wrote...
> > >
> > > > Thanks but that doesn't work too well. The original image is
> > > > noisy and it's not obvious how to choose shades that are distant
> > > > enough to avoid the dithering but not so distant that pixels end
> > > > up remapped to the wrong hue.
> > > >
> > > > And the scaling problem is still there.
> > >
> > > You can just turn off dithering  using  +dither.
> > > In that case -map will just set colors to the closest color found
> > > in the given color map image.
> >
> > This *is* with +dither. It's not FS dithering, it's dithering
> > resulting from noise in the output image.
> >
> Oh I see.  That could be a problem.
>
> Can you crop a small area from the image, containing the various parts
> and send me link.

This is it :

  http://www.teaser.fr/~amajorel/misc/sample.ppm.bz2

For reference, this is the sort of transformation I'm after :

  http://www.teaser.fr/~amajorel/misc/quantise-in.png
  http://www.teaser.fr/~amajorel/misc/quantise-out.png

Yes, the original post mentioned shades of grey and this is just
black and white (and blue). But you get the general idea which is
to turn everything into flat tints. It was done using a
hand-coded program whose gist is :

  if (r < 128 && g < 128 && b < 128) {
    r = 0; g = 0; b = 0;
  }
  else if ((float) b / r >= 1.5 && (float) b / g >= 1.1) {
    r = 32; g = 104; b = 192;
  }
  else {
    r = 255; g = 255; b = 255;
  }

There must be a better way.

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.
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