Reflectance spectra recovery with non-negativity constraints

We propose two methods for recovering the reflectance spectra of given colorimetric data by using the nonnegative constraints in reflectance spectra. We formulate the problem of reflectance spectra recovery as a non-negative least squares problem and solve it with two iterative methods. Experimental results demonstrate that the two methods give similar recovery results, where Macbeth ColorChecker data are used for recovering the reflectance spectra of Neugebauer primary colors. We also transform the recovered reflectance spectra into tristimulus values to visualize them, where an ad hoc scaling operation is introduced for brightening the recovered colors.