Process and apparatus for blending images

Abstract

A process and circuit for blending a foreground image (B) with a background image (A), said foreground and background images being arranged in pixels and having color representations (R, G, B). The foreground foreground image (A) has a transparency parameter (T(x,y)) in accordance with a so-called alpha plane representative of the transparency profile to apply to the foreground image. The process involves the steps of: -applying a dithering method on said alpha plane in order to convert said transparency parameter (T) into a one-bit transparency parameter (T'); -use said one-bit transparency parameter (T′) for controlling a multiplexing unit having two inputs respectively receiving the foreground image (A) and the background image (B). In one embodiment, the one-bit transparency parameter T′ into the two extreme values of a range of continuous values, for instance coded on 8 bits. The process then applies a four-pixel interpolation method to the foreground image (A) for the purpose of creating a five level transparency parameter in the blending process, and then uses the five level transparency parameter for controlling a multiplexing circuit for the purpose of achieving blending of the foreground image with the background image.