identifying COLORS posterized

[stus...@hotmail.com]

+ With the Gimp "posterize" function I am able
to produce an almost real looking image using
16 posterize colors... now my question is,
how can I identify what these 16 colors are ?
Also, I'd need to somehow separate these
to one color layers.
One thing I tried was findinging each color,
using select-by-color, and saving each as an image...
this both did and did not work, as I got far more than
16 selections, and they didnt go back together very
well :)

What I'm after is like separate colors which could
be silk-screened to produce a full color picture.

Anyone done something similar with Gimp ?

[Joal Heagney]

I had a look at a posterised image using Layer -> Colour -> Posterize
(16 Colours) using Layer -> Colour -> Histogram, and it seems that
Posterize just splits the image up into sixteen equal sections through
each of the following channels:
value,
red channel,
green channel and
blue channel.

Whether this represents 16 different colours, or just a reduction to 16
stages in the colour depth would be up to someone else to explain.

Joal Heagney

[Kent Paul Dolan]

stus...@hotmail.com wrote:
> I got far more than
> 16 selections, and they didnt go back together very
> well :)

Look for <image>=>Selection =>Sharpen

This will restrict the selection, as far as I can tell, to
whole pixels with no antialiasing. If you are able also
to posterize with no antialiasing, and use "select by color"
with a tolerance setting of zero, then this will let you
select your image into exactly the N posterized colors,
and they will fit back together on exact pixel boundaries.

However, you must be _obsessive_ about using the
"Sharpen" after each selection, or things go awry, and
the Path to Selection and Selection to Path conversions
break the sharpening, so avoid using them as well.

[It is true, however, that "posterize" creates a lot more
than the user-specified number of colors. By me, this
is a bug, not a feature.]

HTH

xanthian.

[Marc 'BlackJack' Rintsch]

In <1131129763.5...@g44g2000cwa.googlegroups.com>, Kent Paul
Dolan wrote:

> [It is true, however, that "posterize" creates a lot more
> than the user-specified number of colors. By me, this
> is a bug, not a feature.]

You don't specify the number of colors but the number of red, green and
blue levels that can be used. So the minimum setting of two levels means
that each color component can be 0 or 255, resulting in a maximum of 8
colors.

Ciao,
Marc 'BlackJack' Rintsch