COMPOSING AN IMAGE

The invention relates to a computer implemented method for controlling the display of a tile image on a display of the computer device, the method comprising: storing in a computer memory at the computer device, image texture data comprising a plurality of sets of predefined masks, each set of predefined masks for forming a respective tile image; selecting at random a tile image for display from a plurality of tile images; determining a location of each mask in the set of predefined masks for forming the selected tile image, in the image texture data; and supplying an indication of said location to a shader program executed on the computer device to control the shader program to use the set of predefined masks to form the selected tile image on said display. Randomly selected multiple tile images are displayed adjacent to each other to form a background image.