Message values included in a set of valid message values that constitute a coding scheme are each encoded in an image region, called an encoded signal block, composed of a spatially arranged pattern of colored sub-regions. The colored sub-regions have color values produced by modulating a reference color...http://www.google.com.hk/patents/US5946414?utm_source=gb-gplus-share專利 US5946414 - Encoding data in color images using patterned color modulated image regions
