63fb46d6_bster_US___Patent_applications__Description
[Patent application number] 20100098351 [Published] 04-22-2010 [Description] 
SEGMENTATION FOR THREE-LAYER MIXED RASTER CONTENT IMAGES - A method for improving image quality of edge pixels, when separating an image signal into a set of image planes is provided. The method includes searching for a minimum value and a maximum value within at least one predefined neighborhood pixel window centered on a current pixel in the image signal; and conditionally switching the edge pixels to either the minimum value or the maximum value in the foreground and background planes respectively, or to a value of a specified characteristic of the current pixel, based on predetermined criteria. One such predetermined criteria for this conditional switching of the edge pixels comprises comparing the minimum or maximum luminance values in the predefined neighborhood window of the current pixel and their corresponding chrominance values to some predetermined thresholds which are characteristic of the image for the foreground and background planes, respectively.
Xing Li, Webster US - Patent applications