1. A computer-implemented system for digitally compositing a sub-image onto a destination image comprising: an alpha image generator for creating an alpha image of a sub-image from an input image, wherein the alpha image generator separates the sub-image from a background of the input image and providing the alpha image; and a characterizer for determining a first characteristic of the alpha image, the first characteristic being further descriptive of the sub-image; a comparator for comparing the first characteristic with a control box applied to the input image, such that the systems responds to the first characteristic based upon a correlation between the first characteristic and the control box; and an image blender for blending the sub-image in the input image that contains the sub-image onto a destination image using said alpha image, thereby compositing said sub-image and the characteristic of the sub-image onto said destination image.