DIGITAL IMAGE BLENDING ON A PIXEL-BY-PIXEL BASIS

A digital image blending circuit which lets a user draw several planar images and then sum them together with a scalable "blend" function. An image frame butfer (202) is subdivided to store multiple images provided by the user, and the resulting multiple images are combined as a single image within a display window on a pixel by pixel basis by the blender of the invention. The blender (206, 208, 210) of the invention sums the pixel color data on a per-pixel basis, where the pixel data is scaled as a separate operation on color map (205, 207, 209, 211) entries. Control information (BMC) is fed to the blender on pixel boundaries from the frame buffer, and the blender (206, 208, 210) responds to combine the images in accordance with the preferences of the user. As a result, each display pixel may selectively show a single image or a combined image from the associated window. The invention also allows for separate processing of data within each window by defining each pixel with respect to its window boundaries.