Masks with modulated clustering and aperiodicity and rescaling of masks
Patent 6597813 Issued on July 22, 2003. Estimated Expiration Date: 
March 11, 2019. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 11, 2019. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesMethod and apparatus for halftone rendering of a gray scale image using a blue noise mask Digital halftoning space filling curves Clustered aperiodic mask Patent #: 5917951 InventorsApplicationNo. 265861 filed on 03/11/1999US Classes:382/237, Gray level to binary coding358/3.16, Ordered dithering (e.g., deterministic or systematic)358/3.19, Stochastic or random dithering382/205Local neighborhood operations (e.g., 3x3 kernel, window, or matrix operator)ExaminersPrimary: Coles, Edward L.Assistant: Mitchell, Monica Attorney, Agent or FirmInternational ClassesG06K 009/36G06K 009/56 G06F 015/00 AbstractA technique combines most of the advantages of both blue noise and clustering in generating a partially clustered aperiodic mask and using it in a dither array algorithm for halftoning, such that the amount of clustering can be modulated. A method to create an enlarged partially clustered aperiodic dither mask, appearing as a modulated version of a periodic enlargement of original mask, is used when the original mask generates patterns that are not visually pleasing or the original mask doesn't generate enough distinct grey levels. The method of halftoning of grey scale images utilizes a pixel-by-pixel comparison of the image against a partially clustered aperiodic mask in which the clustered aperiodic mask is comprised of a partly random and partly deterministic single valued function which is designed to produce visually pleasing dot configurations when thresholded at any level of grey. A method for changing a number of distinct grey levels a mask can produce to be used in halftoning of grey scale images produces advantages for some printing devices.Field of SearchIMAGE COMPRESSION OR CODINGGray level to binary coding Local neighborhood operations (e.g., 3x3 kernel, window, or matrix operator) Ordered dithering (e.g., deterministic or systematic) Clustered pattern Dithering (e.g., spatial distribution of print elements by threshold matrix) Screen property or geometry (e.g., shape, period, symmetry, aspect ratio) Stochastic or random dithering | |
