[argyllcms] Re: Argyll/Spyder2 Help needed

Am 26.11.2011 00:18, schrieb Graeme Gill:
Hendrik Helwich wrote:
i am new to color management coding and bought me a Spyder 2 which i got
easily working with argyll on Ubuntu 10.04 which is very cool :-)

I want to measure the spectral impact of some color filters i have
(anaglyph glasses).
Hi,
        I doubt the Spyder is the right tool for spectral characterisation.
The Spyder is a colorimeter, not a spectrometer, and it's a colorimeter that's
tuned for particular displays, rather than being general purpose.

Hi,

probably you are right, but i will try how far i come with that tool :-)
It was not very expensive on ebay and i guess spectrometers will be more expensive. I am doing this just for fun and because i am not satisfied with some anaglyph method results.

My idea is to display a set of RGB colors on my LCD monitor and measure
them with the spyder (e.g. in XYZ color space). Afterwards i want to
measure the same RGB colors again but with a color filter between the
LCD and the spyder. All the collected informations should be stored in
some kind of text file.
It's doable, and may be useful if the intent is to use the glasses on
that particular display. It's less useful if you want to predict
the effect of the glasses in some other situation.

The colorimeter is giving the colors in XYZ space which should be device independent as i think. So the approximated color filter function should have its input and output values in XYZ color space and would also be device independent. But the measured data will only be a subset of the whole physically possible colors because of the limited gamut of the LCD. Maybe its possible to collect measurement data with different LCDs and different monitor setups to cover at least the possible gamuts of different LCDs. But for printing i think this could get inaccurate.

Now i could develop an application which reads the data and estimates an
approximation function for the color filter.
Do you have a copy of this article ?
<http://www.imaging.org/IST/store/epub.cfm?abstrid=43659>

No - thank you for the hint. This sounds very promising. But i do not want to pay for this PDF without knowing if i could use the content. It would be nicer if he would share his findings with the community like others do ;-)
But if somebody has a copy of it i would be glad if i could get it.

Is it possible to give argyll a set of RGB values which should be
displayed and measured (e.g. in XYZ color space) and store the measured
values to a file?
You can do this manually using a combination of dispwin and spotread
easily enough.  See<http://www.argyllcms.com/doc/dispwin.html>
and<http://www.argyllcms.com/doc/spotread.html>.

This works well with spotread. Thank you!
I am calling it with:
> spotread -y l
And get the following output for a white color:
> Result is XYZ: 132.247557 139.842979 120.663127, D50 Lab: 113.719384 -3.601868 -3.378244
Are these XYZ values in a relative or absolute form?

It works well in the shell but i have a problem if i call spotread from Java:
> spotread: Error - tcgetattr failed with 'Invalid argument' on stdin
I assume its not possible to use spotread without a shell and to tell it to read its input from a stream instead?

If this is not possible, could you please give me a hint how to access
the spyder2 with an own application based on the argyll spyder2 code? It
would be sufficient for me to trigger the spyder to measure a color an
return the result.
Look at the spectro/inst.h for the instrument API (but please
note the GNU license if you are building it into some other application).

Ok.
I also want to release my code under a GPL license if it gets useful someday.
Thank you for sharing your great work and knowledge with others :-)

Best regards,

Hendrik

Graeme Gill.





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