Spectral and XYZ Color Functions

Label plots with spectra. Convert wavelengths to RGB. Functions for color matching and illuminants.

Description

This is the beginning of a set of functions for working with color as wavelengths (spectral color) and in the xyY and XYZ color spaces.

Current functionality includes:

spectrumLabel - Add a color bar containing the visible spectrum to a plot's X axis.

spectrumRGB - Converts wavelengths of light to equivalent RGB values (in the sRGB space).

colorMatchFcn - Raw data of popular color matching functions (spectra to XYZ) for various standard observers:
  * CIE 1931 2-degree
  * CIE 1964 10-degree
  * CIE 1931 2-degree modified by Judd (1951)
  * CIE 1931 2-degree modified by Judd (1951) and Vos (1978)
  * Stiles and Burch 2-degree (1955)
  * Stiles and Burch 10-degree (1959)

illuminant - Raw data for the A, D65, and E standard illuminants.

• Acknowledgements: This submission has inspired the following:; Perceptually improved colormaps , MKPJ - perceptually improved Jet colormap
• Required Products: Image Processing Toolbox
• MATLAB release: MATLAB 7.0.1 (R14SP1)

[Wu John]

Good job! Thank you,but how about the other light source in illuminate.m?

[colour rainbow]

could you able to create function for r2xyz
for 1xm or 1xn matrix

[marwan reyadh]

please how can i convert an image from RGB of size n*n*3 to an image with of size n*n*n

[Levent Onural]

Thanks a lot, I have been looking for how I could generate the matching functions for 5 hours. Excellent piece of work...

[ben taylor]

Does anyone know hot to convert it the other way? I have an RGB image of black body radiation and I am writing a program that will give me a 3d temperature plot, but I need to convert from RGB to wavelength to temperature.

Thanks,

[Vishnuvenkatesh Dhage]

 

[NOne None]

None

[jeongwoon lee]

 

[Neeraj Adsul]

 

[Franck Riberi]

Need demo files absolutely.

[Mike Vasilescu]

how do I get the spectrumon jpg?

[Matteo Niccoli]

Great submission!

[springface]

Thanks to this excellent work, I've been able to image a spectrum plot with both the characteristic peaks marked in colors and intensity plot shown. The code is as following.

%%%%%%%%%%%%%%%%%%%%%%
function SpecRGB_Intensity(wavelength,intensity, peak_threshold)
% wavelength and intensity are vectors
% the characteristic peaks are chosen if the value of the peak
% is bigger than the peak_threshold.
% by springface

sRGB = spectrumRGB(wavelength);

%% Transform spectrum plot into an image, marked by colors
len_wave = length(wavelength);
len_inten = 1000;
intensity_plot = max(intensity):-max(intensity)/(len_inten-1):0;
wavelength_plot = wavelength;

intensity_num = ones(size(intensity));

for cc = 1: len_wave
    if intensity(cc)>=0
        [C,I] = min(abs(intensity(cc)- intensity_plot));
        intensity_num(cc) = len_inten-I;
    end
end

im_plot = ones(len_inten,len_wave,3);

for cc = 1: len_wave
    im_plot(1:intensity_num(cc),cc,:) = repmat(sRGB(1,cc,:),intensity_num(cc),1);
end

%% mark the non-peak area as black
spec_idx = intensity < peak_threshold;
sRGB(1,spec_idx,:) = zeros(1,sum(spec_idx),3);

%% Plot figures
figure;

whitegap_len = 2;
RGBspec_len = 100;

RGBspec_range = max(intensity)+whitegap_len+RGBspec_len+1:max(intensity)+1;

imagesc(wavelength_plot,[RGBspec_range,intensity_plot],...
    cat(1,repmat(sRGB,RGBspec_len,1),ones(whitegap_len,len_wave,3),im_plot));
set(gca,'YTick',[])
%%%%%%%%%%%%%%%%%%%%%%

[springface]

but there seems to be a scale off. I don't know how to solve that. Please help!

[Li]

I got this error information:
"the selected cell cannot be evaluated because it contains an invalid statement".
"??? Input argument "formulary" is undefined."
Any idea why this happen? Thank you!

[Guido]

Help!
I'm trying to use spectrumLabel for a calculated absorption spectrum.
It works fine from the command window, but I'm not able to put the color axis in a plot which is rendered to a GUI.
Here is the piece of code that I put in the .m file. The plot of the extinction, scattering and absorption spectra are sent to the axes style GUI handles.axes1:
----------------------------
axes(handles.axes1);
plot(wave,qext,wave,qsca,wave,qabs);
title('Spectrum');
xlabel('Wavelength (nm)');
ylabel('Arbitrary units');
spectrumLabel(handles.axes1);
-------------------------------
Apparently, the spectrumLabel is put at the right position but with zero or very small vertical dimension.
Thank you!