An image is divided into one or more (e.g., foreground) regions of interest with transition regions defined between each region of interest and the relatively least-important (e.g., background) region. Each region is encoded using a single selected quantization level, where quantizer values can differ...http://www.google.de/patents/US6256423?utm_source=gb-gplus-sharePatent US6256423 - Intra-frame quantizer selection for video compression
