63fb46d6_bster_US___Patent_applications__Description
[Patent application number] 20100142806 [Published] 06-10-2010 [Description] 
3 + 1 LAYER MIXED RASTER CONTENT (MRC) IMAGES HAVING A TEXT LAYER AND PROCESSING THEREOF - A method, system and data structure for providing a 3+1 layer MRC image, including a text layer. The text layer includes pixel data corresponding to text in an image and may be assigned a predetermined value for a particular color. According to one or more embodiments, the 3+1 layer MRC image may be subject to clean-up processing to alter one or more of the layers, other than the text layer, based on the text layer pixel data. This clean-up processing reduces redundant information stored in the 3+1 layer MRC image and provides opportunities for file size reduction (i.e., data compression).
Xing Li, Webster US - Patent applications