Re: [Gimp-print-devel] [utx@k332.feld.cvut.cz: Re: Colormanagement]

[<sh...@al...>]

> Note: I think that colormanagement library should not include only ICC profiles.
> It should include "simple" way based on phospors chromaticity
> and white point for CRT and on C, M, Y, CM, CY, MY and K
> chromaticity for print.
> Ghostscript and PostScript Language Reference Manual is a good source for such
> coding.
> Much worse is to obtain basic chromaticity data (i. e. data for different
> monitors and inks).

I don't think we need to worry too much about monitor variations.  Even
if we could get a published number for phosphor colors, they'd only be valid
for one particular setting of the brightness/contrast controls, ambient
lighting conditions, and monitor age.  Sometimes there are also positional
dependencies on color.  A pixel on the center of the screen isn't necessarily
the same color as a pixel near the edge, nor would it appear to be even if
it was due to the proximity of a (usually) white plastic bezel around the
screen.  All of these things need to be taken into account for precise
color representation.

I think that's beyond our scope and not a good use of our resources to try
and cope with all of that.

There is a published standard called BT. 709 which is what CRT manufacturers
have been supposed to conform to since 1990.  The text of this standard is
not freely available on line, AFAIK, but you can order a copy.

However, you don't really need the official spec.  The essentials of the
BT. 709 color specification are covered in both of the following:

  The Color FAQ (Charles Poynton) 
  http://www.inforamp.net/~poynton/ColorFAQ.html

  The W3 Consortium Standard for Color (co-authored by Microsoft and HP)
  http://www.w3.org/Graphics/Color/sRGB.html

I think we should simply try to follow these standards, and hope that monitor
manufacturers also do a good job of conforming to this specification.

As far as ink colors, I don't think there's quite such a standard.  Most
printers have proprietary drivers for conversion of RGB to the printer's
native ink set.  Getting this information is the most difficult part.

Eric