Imaging the Pigments of Human Skin with a Technique which is Invariant to Changes in Surface Geometry and Intensity of Illuminating Light

Abstract: A technique is described which enables quantitative histological data to be recovered from conventional digital images. Methodology is developed around the concept of image ratios, which are shown to be invariant to scene geometry and illumination intensity. Key to the success of this technique, is a function which maps uniquely from a vector if image ratios to the corresponding vector of histological parameters. The existence of this function is established using mathematical techniques drawn from differential geometry. The methodology is formulated generally then applied to a two-parameter model of human skin. A function relating image ratios to concentrations of melanin and blood is established and used to process a standard RGB image. The technique successfully maps out the distribution of blood and melanin across the entire image.