1. A method of generating an alpha matte from an image comprising image forming elements each of which has a respective value, the method comprising operating a physical processor to perform operations comprising for each of one or more of the image forming elements: determining a respective representative foreground value from one or more of the image forming element values; normalizing the respective representative foreground value and the value of the image forming element with respect to a threshold level; and generating a respective value of the alpha matte from an evaluation of the normalized image forming element value in relation to the normalized representative foreground value.