In article <GvsPOYQ0gONAxo4TzcbW6gmRbpjF@4ax.com>, Glen Berry 
<7no### [at] ezwvcom> wrote:

> >posterize
> 
> As Ron Parker described, classic posterization is simply reducing the
> color depth to a relatively small number, without using any dithering
> to hide the banding. I don't believe that one has to perform this in
> two passes, however. Simply divide the range between minimum allowable
> value (0), and maximum allowable value for a color into a few discrete
> ranges. Posterization is basically a color depth adjustment, where you
> get to specify any number of possible shades between 0 and 255. For
> example, a setting of "5" would allow 5 different shades of red, 5
> shades of green, and 5 shades of blue. If you wanted to get a little
> fancier, you could specify different depths for the different color
> channels.

This is exactly what is done with my "steps" filter. I multiply the 
float colors by a certain amount, convert to integer, and then scale 
back to the original color range. And it is already per-channel, you can 
have different numbers of steps for each channel.


> >solarize
> 
> Solarize can be achieved with an "iso-function" type patch. Basically,
> if a pixel exceeds a certain value, it is converted to a "negative"
> image.
...
> This generates a fixed response curve that makes a negative image of
> anything above the mid-point of the scale. It's a deep and dramatic
> solarization effect. A more refined approach would be to offer a user
> specified value for the reversal threshold.

Hmm, this will probably stay in the "to do" pile for a while.


> I would *highly* reccomend you visiting this site:
> 
>    http://www.tisl.ukans.edu/~jgauch/kuim/
...

Thanks for the link!

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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