Get CIEL*a*b* values from DataColor .QTX files

[Bob]

Hello,

I would like to extract Lab values from a .QTX file of DataColor. Do you
know any code or a tool that could do this?
It is important that I get directly Lab values, and not spectral datas.

Thank you very much in advance.

Bob.

[Danny]

QTX is a tagged ASCII file. So open the file in a good text editor
(notepad may not be powerful enough - but there are many shareware
editors). Then do a search for the Lab tag(s) and extract those lines.
You could do this in Excel if you can create macros.

[Bob]

Thank you very much for your answer Danny.

You're right, I've managed to open it with a text editor. But the problem
is that, my QTX file has no Lab tag, I can only find spectral datas.
Does someone know a tool, or any code that could compute Lab values from
those spectral values ?

Thanks a lot in advance.

Bob.

"Danny" <Dann...@softhome.net> a écrit dans le message de
news:1131123183....@g14g2000cwa.googlegroups.com...

[timo.au...@aim-dtp.net]

Bob wrote:

> Does someone know a tool, or any code that could compute Lab
> values from those spectral values ?

If you have Excel you can do this very easily using my AIM.XLA from
http://www.aim-dtp.net/aim/technology/aim_xla/index.htm it is an Excel
Add-In for spectral and colorimetric calculations, freeware.

Timo Autioakari

[Bob]

Hello Timo,

Thanks a lot for your reply.

Actually I would like to develop C routines to do this, do you have formulas
that I could use, or C code ?

Thank you in advance.

Bob.

<timo.au...@aim-dtp.net> a écrit dans le message de
news:1131355852.2...@g47g2000cwa.googlegroups.com...

[Timo Autiokari]

"Bob" <nos...@nospam.com> wrote:

>Actually I would like to develop C routines to do this,
>do you have formulas that I could use, or C code ?

You can find the formulaes e.g. on the http://www.brucelindbloom.com/
press the Math button there.

Timo Autiokari

[Bob]

Thank you very much Timo.

I'm not very good in mathematics, if someone knows some direct conversion
spectral to Lab code that would be great for me.

If no, I have complementary questions about the formulas on
http://www.brucelindbloom.com :
-where could I find the CIE standard observer functions ?
-where could I find the spectral power distribution of a reference
illuminant like D65 ?

Thank you very much in advance.

Bob

"Timo Autiokari" <timo.au...@aim-dtp.net> a écrit dans le message de
news:ec3vm1hsi37diiff2...@4ax.com...

[Gernot Hoffmann]

Bob,

color matching functions x-bar... and daylight Dxx-data are here:
http://www.fho-emden.de/~hoffmann/cie-data.txt

Should be shown by Courier New by WordPad.
Only up to 700nm.

Best regards --Gernot Hoffmann

[timo.au...@aim-dtp.net]

Bob wrote:

>if someone knows some direct conversion spectral
>to Lab code that would be great for me.

There are no "direct conversion code" for spectra to Lab. Lab is just
an inferior transformation (contortion) of the CIE XYZ. You need to
convert the spectral reflectance data first to XYZ and then, in case
you really do need it, convert the XYZ to Lab.

> -where could I find the CIE standard observer functions ?
> -where could I find the spectral power distribution of a reference
> illuminant like D65 ?

You'll find them and a lot more from the Colour & Vision database here:
http://cvrl.ioo.ucl.ac.uk/

Timo Autiokari

[Bob]

Thanks a lot Timo and Gernot !
I will study all this.

Have a good day.

Bob.

<timo.au...@aim-dtp.net> a écrit dans le message de

news:1131518464.7...@f14g2000cwb.googlegroups.com...

[jcam...@americhem.com]

There is a free (for personal non-industrial use {as if people use
spectros at home...wait a minute... actually I do!}) software at
Clariant called 'MatchWizard Lite 2004'. It can import and display
*.qtx files.

[jcam...@americhem.com]

sorry
MatchWizard Lite 2003 Edition.