A system and method for scaling a composite overlay image, wherein the composite overlay image comprises a plurality of pixels and each pixel comprises at least one color channel and at least one alpha channel, and further wherein at least one pixel of the composite overlay image has an alpha value of zero and a colour value that is not well defined. First, a set of pixels of the composite overlay image are identified as pixels to be dilated. The color channels of the identified pixels are then dilated to form dilated composite overlay image. Finally, the dilated composite overlay image is scaled.