Ken, I followed your suggestion and perhaps I don't understand what to expect from convertColor or maybe I'm not using it correctly. Consider the following tests:
D65 <- c(0.3127, 0.329, 0.3583) # D65 chromaticity coordinates X <- D65[1]*D65[3]/D65[2] # conversion per brucelindbloom.com Y <- D65[3] Z <- D65[3]*D65[3]/D65[2] XYZ <- data.frame(X = X, Y = Y, Z = Z) # D65 in tristimulus values (?) colnames(XYZ) <- c("X", "Y", "Z") tst1 <- convertColor(XYZ, from = "XYZ", to = "sRGB") tst2 <- convertColor(D65, from = "XYZ", to = "sRGB") # none of these are 1,1,1, namely white (they are ~ 0.6, 0.6, 0.6) So it looks like D65, a white standard, does not come back to something near white in the sRGB space. What am I doing wrong here, or what do I misunderstand? Please don't say everything! Thanks, Bryan On Jun 12, 2013, at 2:57 PM, Ken Knonlauch <ken.knobla...@inserm.fr> wrote: > Bryan Hanson <hanson <at> depauw.edu> writes: > >> >> grDevices::convertColor has arguments 'from' and 'to' which can > take on value 'XYZ'. Can > someone confirm >> that 'XYZ' is the same as the CIE chromaticity coordinates > are also sometimes refered to > as 'xyY' in >> the literature? Or are these the CIE tristimulus values? > It looks to me like the first case is > true, but I >> would appreciate hearing from one of the people in > know. Thanks, Bryan >> >> > > I.'d look at the code or put in some known data to test it, > but XYZ are tristimulus values and xyY are chromaticity > coordinated and the luminance which is the Y tristimulus > value for the CIE 1931 standard observer. > > Ken > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.