1. A method of representing an image, using one or more processors, comprising: deriving, using a processor, at least one descriptor based on colour information and colour interrelation information for at least one region of the image, the descriptor being derived using values of pixels in said region and having a plurality of descriptor elements, wherein at least one descriptor element captures colour information which represented a pixel average using values of pixels in said region, and at least one descriptor element captures colour interrelation information which represents a difference between two averages of pixel values in said regions, and wherein said average and said difference are calculated in said regions at different location.