1. A method for estimating a visible vector representation for pixels in an infrared image, the method comprising: receiving an infrared (IR) image captured using a N-band infrared imaging system, said IR image comprising a plurality of pixels with each pixel having an IR band vector of N intensity values collected for that pixel; and for each pixel of interest in said infrared image: using a search metric to search a spectra database of vector samples to identify a visible-IR set with intensity values closest to this pixel's IR band vector, where said visible-IR sets and said intensity values in the IR band are narrowband spectra, said search metric comprising: where N is the number of spectral bands of said imaging system, N cIR is the number of samples in said visible-IR set, S IR x cIR (λ i ) is the IR reflectance of sample x cIR from the visible-IR set at wavelength λ i , and S IR x IR (λ i ) is the IR reflectance of sample x IR from the IR set at wavelength λ i , with a visible portion of x cIR being assigned to sample x IR ; and estimating a visible vector representation for said pixel based upon the visible portion corresponding to said closest visible-IR vector.