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List:       kde-kimageshop
Subject:    color models
From:       Matthias Elter <me () main-echo ! net>
Date:       1999-08-16 7:29:12
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Hi

I have done some research into color models in the last week. IMO we should
support:

- bitmaps (black/white)
- grayscale (256 gray values)
- indexed colors (max. 256 colors, mapped to RGB space by a color table)
- RGB
- LAB
- HSV/HSB
- CMYK

I have code to convert between RGB/LAB/HSB/CMYK in KColor (LAB and CMYK to be
commited today). The reason why I think we should support these models are:

- RGB: basic additive color model, we simply need it. ;-)
- CMY(K): A subtractive color model. Most output devices like your printer at
home have cyan/magenta/yellow and black as base colors. CMYK is very important,
as no output device can generate all RGB colors.
- HSB/HSV: Hue/Saturation/Brightness. Is not really a independant color model,
it describes the RGB space in a more human readable way.
- LAB: a device independant color space description. LAB color space is bigger
than RGB or CMYK. It's the native color model of PostScript Level 2 and has
many advantages.

Coverting from RGB to CMYK does not decrease quality. -> We can use RGB filters
and plugins on CMYK images, by simply converting to RGB, applying the filter 
and then back to CMYK.

Converting from LAB to RGB does in theory loose quality because LAB color space
is bigger than RGB but it is not really a problem as there are no output
devices that support the full LAB color space and your monitor can not even
display the full RGB space. LAB is mostly used for convenience as you can do
some manipulations easier in LAB than in RGB. We are going to use RGB filters on
LAB, the same way as for CMYK.

Do you agree? Is something missing? Has somebody knowledge of color management
systems? Are there open standards? Are these icmp or icc files binaries?

Greetings, Matthias

--
Matthias Elter
me@kde.org / me@main-echo.net
KDE developer

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