63fb46d6_bster_US___Patent_applications__Description
[Patent application number] 20090238489 [Published] 09-24-2009 [Description] 
EDGE TRANSITION DETECTION IN A HIGH-ADDRESSABLE ERROR DIFFUSION ENVIRONMENT - What is disclosed is a novel system and method for edge transition detection when improve print quality when rendering via high-addressable vector error diffusion in an image processing environment. In order to detect an “ideal” edge and compensate for the adverse effects described in the background hereof, local pixels are detected and local gradient values are calculated and compared against an adjustable threshold to determine the interpolation method needed for that particular pixel. A nearest neighbor interpolation is performed when a local gradient exceeds a predetermined threshold. For example, if the difference between two successive pixels is greater than “200”, nearest-neighbor interpolation is used to calculate the intermediate sub-pixel level(s). Otherwise linear interpolation is used. Dynamically switching between these two interpolation schemes significantly improves the integrity and sharpness of the edges. There is no loss of error information distributed to downstream pixels thereby preserving the gray integrity of the input.
Xing Li, Webster US - Patent applications