1. An illumination normalizing apparatus, comprising: a discontinuity measuring means, measuring a discontinuity of each pixel of an input image, the discontinuity comprising a spatial gradient and a local inhomogeneity; a weight calculating means, producing a weight of each pixel from the discontinuity by using a transfer function; an illumination estimating means, producing an estimated illumination by repeating a convolution operation on each weight; and an illumination normalizing means, subtracting the estimated illumination from the input image.