Re: How do I make my colors _perfect_?

On Tue, 17 Dec 2002 [email protected] wrote:

> I need to have accurate color representation on my monitor.  Of course
> monitors and video cards differ in this area, so how do I know a color
> being presented to me on the screen is true to the color of the source?
> 
> Is there any way to "tune" the Xserver to display colors accurately on
> a given monitor?

Xcms is the only existing technology for this that I'm aware of -
"man xcmsdb XcmsCreateCCC" may be a reasonable starting point.

I believe that Keith Packard thinks that it should be replaced.
Here is a list of things I've learnt about Xcms over the years:

1) Client apps have to be aware of Xcms to use it.

2) Xcms uses its own trig routines for Polar<->Cartesian conversion
between color-spaces*, and these are buggy. Someone once sent me a patch
for XFree86 3.3 which helped, but my tests suggested that it wasn't a
complete fix, and I've never submitted it.

*I think TekHVC suffered the most from this.

3)
I have a program
	http://www.dpmms.cam.ac.uk/xfree86-devel/ddc2xdccc.c
which converts the color calibration from the monitor's DDC output
into a format which xcmsdb can read, but my experience, and perceived
wisdom, is that on average using the default setup gives more accurate
color than trusting the info provided by the monitor itself :-(

-- 
Dr. Andrew C. Aitchison		Computer Officer, DPMMS, Cambridge
[email protected]	http://www.dpmms.cam.ac.uk/~werdna