Lossy compression of partially masked still images

Summary form only given. This article describes a component of the DejaVu color document image compression. The DejaVu scheme consists in separating the image into (a) a foreground layer containing text and drawings, and (b) a background layer containing background color and the pictures. These two components are then compressed using the most appropriate techniques. This article outlines a wavelet method for encoding the background layer without wasting bits on pixels masked by the foreground layer. Our method handles arbitrarily complex masks with reasonable computational requirements.