1. An apparatus for imaging a biological sample, comprising: an input configured to receive at least one of imaging data acquired from and an image of the biological sample; and a processor configured to receive the at least one of the imaging data and the image from the input, the image characterized by a first chromaticity parameter and a first transmission spectrum, to enhance spectral signals associated with the at least one of the imaging data and the image to form an enhanced transmission spectrum, and to apply a linear transform to the enhanced transmission spectrum using estimated transmission data and training data to generate a digital representation of a physical reaction of the biological sample to a target chemical stain having a first chemical structure and with which the sample has not been physically stained, said digital representation corresponding to a target image characterized by a second chromaticity parameter that is different from the first chromaticity parameter.