A whitening transformation for two-color blood cell images

An image enhancement technique is described for the preprocessing of stained white blood cell images which have been digitized through two different color filters from either end of the visible spectrum. Typically, corresponding picture elements (or pixels) from blood cell images digitized in this manner exhibit slight changes in grey-level due to the color filtering, but remain strongly correlated in optical density with each other. Also, color and density information are interrelated in the pixels of both of the filtered images. The technique described is a whitening transformation on the bivariate distribution of image pixels, this results in two uncorrelated axes, one relating to density and the other relating to color. The spatial effect on the two original images is to produce two separate, transformed, “color” and “density” images.