Illumination correction and contrast equalization in colour fundus images

A method for correction of non-uniform illumination in colour fundus images based on the B-spline approximation of the illumination surface is presented. The control points for B-splines are determined from an original image, separately from the red, green and blue channel. The estimated illumination surface is used in a multiplicative model for fast correction. The proposed approach has been subjectively tested on new publicly available retinal image database DRIIL (Digital Retinal Images for ILumination correction), which contains 165 images. Objective testing has been conducted by investigating the influence of the proposed method on blood-vessel segmentation using another high resolution fundus image dataset of healthy and diabetic patients.