Transparency information in image or video format not natively supporting transparency

摘要

Colour information and transparency information of pixels of a source image, which may be a partially transparent overlay image of a format that natively support transparency, are stored as a transformed image. The transformed image is of a format that does not natively support transparency. The transformed image has two disjoint regions, one storing the source color information and the other storing the source transparency information. The transformed image can be used as a representation of the overlay image when compositing with a base image.