Topic: non-Gaussian structure

We study the statistics of the 3D color space of natural images and develop a model for efficiently representing this structure. Analysis of a dataset of 503 calibrated natural images reveals striking non-Gaussian structure with heavy tails in distinct directions that are asymmetrically distributed in 3D color space. An overcomplete, non-negative sparse coding model adapted to this structure recovers a basis aligned with the directions of black, white, red, green, blue, and yellow - i.e., the 'unique hues' that are proposed to constitute a psychological basis for color appearance. Moreover, th