Hi Marti, Thank you for all of your help thus far. Seeing what you were attempting to do with scaling the XYZ numbers in the spreadsheet was very enlightening. From what I learned, I used the XYZ numbers from the RGB(0, 0, 0) to RGB(255, 255, 255) measurements to offset and scale the remaining XYZ numbers from XYZ(0, 0, 0) to XYZ(monitor's white point), which made quite a difference, because once that was done and converted to Lab, and then transformed to RGB using lcms and the monitor's profile, the difference between the displayed RGB and the calculated RGB (from actual measurements) was impressively small.
I would prefer to use the XYZ data for the RGB(0, 0, 0) and RGB(255, 255, 255) measurements taken during the profile creation (i.e. that seen in the IT8-formatted area between BEGIN_DATA / END_DATA sections inside the .icc file) to do the scaling so I do not need to re-read the black and white swatches each time I want to measure a color on the monitor in order to properly scale it. By using the RGB(0, 0, 0) and RGB(255, 255, 255) measurements taken during the profile creation, I will also be able to see if the brightness of the monitor has drifted or was changed since the profile was created. Can I be assured that this data is embedded in monitor profiles? If so, which lcms functions can be used to retrieve this data? The lcms IT8 functions do not appear written to parse IT8 data out from the middle of an ICC profile. I have also been attempting to use lcms to get the 'lumi' data from the profile, but I have been unable to determine which, if any, of lcms's exported functions will return the data for the icSigLuminanceTag tag. But even then, I understand that all you are guaranteed to get is the raw and unscaled Y value, with no guarantee of getting the X and the Z values, which may in fact be set to zero. I attempted to scale the X, Y, and Z values using only what Kai-Uwe Behrmann told me the profile's luminance value was (116), which resulted in adequately scaled Y values, but not so adequately scaled X and Z values, resulting in some significant error. So, how can I retrieve the absolute measurement data for the black and white swatches from the profile? If I can not do that, how do I get the absolute luminance data from the profile? Thank you again for all of your time, Michael A. Litscher CTO, ColorMetrix Technologies, LLC ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
