Blending graphics objects in a frame buffer

Abstract

Methods and apparatus that blend graphics data. In a printing device, a first object is received and rendered into a frame buffer; a second object including blending instructions is received for blending with the first object; and rendered data associated with the first object is retrieved from the frame buffer and a blend of the two objects is rendered according to a user-selectable blending algorithm. The frame buffer may be a deep frame buffer. The blended data printed may be of a bit depth reduced from that of the frame buffer. The reduced bit depth may be achieved by halftoning the blended data. The blending algorithm may be transparency, shadow, overprinting, darkening, lightening, screen effect or additive effect. The blending instructions may include a blend operator defining a blend algorithm for blending two objects. In another aspect, a printing device includes an interpreter for receiving object data associated with a background and a foreground of an image; a render engine for rendering object data; a frame buffer for storing rendered data; and a blend processor for retrieving rendered data from the frame buffer and for blending it with rendered data from a foreground object prior to printing. The printer may be configured to receive a page description language description of a page to be printed.