IMAGE PROCESSING APPARATUS, IMAGE PROCESSING METHOD, AND MEDIUM STORING IMAGE PROCESSING PROGRAM

A reflectance image that represents a reflectance distribution, and an illuminance component image that represents an illuminance distribution are generated from an input image. A plurality of small regions, which are divided based on illuminance components of the generated illuminance component image, are specified. A quantized image is generated from the reflectance image for respective specified small regions. Regions having equal quantized pixel values are acquired in the quantized image. Representative pixel values for the respective acquired regions are acquired based on the illuminance component image. Quantized pixel values of the respective acquired regions are corrected using the acquired representative pixel values.