The piecewise-constant image model

The piecewise-constant image model (PWC) is a new technique for lossless compression of palette images. PWC is a blend of traditional scanline-oriented and newer object-based methods. Remarkably, PWC delivers the best known compression across a wide variety palette of image types while delivering translation speeds comparable to highly tuned one-dimensional methods. This paper introduces the topic of palette image coding and traces the development of the piecewise-constant model from a completely object-oriented code requiring two image passes to a high-performance scanline-oriented code.