Photometric correction of retinal images by polynomial interpolation

This paper presents a photometric restoration technique that automatically corrects shading within retinal images taken with a fundus camera. The proposed technique is based on the observation that the background of retinal images usually shows flat reflectance variations due to its high similarity in color and texture. It estimates shading through an iterative polynomial interpolation procedure that first estimates a shading image through a horizontal interpolation process and then improves the shading estimation by a vertical interpolation process. Once the shading image is estimated, a reflectance image can accordingly be determined based on the luminance of the retina image under study. Experiments on 161 retinal images of different qualities show promising results.