Halftone method and apparatus that provides simultaneous, multiple lines per inch screens
First Claim
Patent Images
1. A printer system, comprising:
- a scanner for scanning an input image;
a memory, coupled to the scanner, for storing a scanned image;
a halftoning processor, coupled to the memory, for processing the scanned image in the memory according to a halftone threshold matrix, the halftoning processor deciding on a level for a pel depending upon the halftone threshold matrix and the scanned image and generating an output based upon the decision, the halftone threshold matrix comprising a supercell divided into a plurality of subcells, the plurality of subcells comprising at least a first group of N×
M subcells having a first line frequency and a separate and distinct second group of A×
B subcells having a second line frequency, wherein a size of the first and second group of subcells are not equal, and wherein more than one pixel in a first subcell is turned on before a next pixel in a second cell is turned on; and
a printer for receiving the output of the halftone processor and generating a printout in response thereto.
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Abstract
A halftone threshold matrix includes a plurality of submatrices, wherein a first group of the plurality of submatrices has a line screen frequency different from a second group of the plurality of submatrices. The halftone method and apparatus removes the restriction that at most one pel is turned on per basic cell for the next constant input level and allows the pels in some basic cells to be turned on much sooner that the corresponding positions in other basic cells. This creates a dominant low frequency line screen simultaneously with the higher frequency line screen of the other basic cells. The present invention also allows the basic cells inside the threshold matrix to have different shapes and sizes. Thus, the cells participating in the low frequency screen could be larger than the cells generating the higher frequency screen. For example, the low frequency screen'"'"'s pleasing patterns can distract the eye from noticing less pleasing patterns in the high frequency grid and vice versa.
25 Citations
13 Claims
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1. A printer system, comprising:
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a scanner for scanning an input image; a memory, coupled to the scanner, for storing a scanned image; a halftoning processor, coupled to the memory, for processing the scanned image in the memory according to a halftone threshold matrix, the halftoning processor deciding on a level for a pel depending upon the halftone threshold matrix and the scanned image and generating an output based upon the decision, the halftone threshold matrix comprising a supercell divided into a plurality of subcells, the plurality of subcells comprising at least a first group of N×
M subcells having a first line frequency and a separate and distinct second group of A×
B subcells having a second line frequency, wherein a size of the first and second group of subcells are not equal, and wherein more than one pixel in a first subcell is turned on before a next pixel in a second cell is turned on; anda printer for receiving the output of the halftone processor and generating a printout in response thereto. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for halftoning an image using a multitone printer, comprising:
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scanning an image; deciding on a level to be printed at each pel using a halftone threshold matrix comprising a supercell divided into a plurality of subcells, the plurality of subcells comprising at least a first group of N×
M subcells having a first line frequency and a separate and distinct second group of A×
B subcells having a second line frequency, wherein a size of the first and second group of subcells are not equal, and wherein more than one pixel in a first subcell is turned on before a next pixel in a second cell is turned on; andprinting pels based upon the decision.
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13. An article of manufacture comprising a program storage medium readable by a computer, the medium tangibly embodying one or more programs of instructions executable by the computer to perform a method for halftoning an image using a multitone printer, the method comprising:
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scanning an image; deciding on a level to be printed at each pel using a halftone threshold matrix comprising a plurality of submatrices; deciding on a level to be printed at each pel using a halftone threshold matrix comprising a supercell divided into a plurality of subcells, the plurality of subcells comprising at least a first group of N×
M subcells having a first line frequency and a separate and distinct second group of A×
B subcells having a second line frequency, wherein a size of the first and second group of subcells are not equal, the method further comprising deciding to turn on more than one pixel in a first subcell before a next pixel in a second cell is turned on; andprinting pels based upon the decision.
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Specification
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Current AssigneeRicoh Company Limited
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Original AssigneeInternational Business Machines Corporation
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InventorsQiao, Yue, Mitchell, Joan LaVerne, Dittrich, Danielle Kathryn
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Primary Examiner(s)Moore; David
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Assistant Examiner(s)Thompson; James A.
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Application NumberUS09/571,181Time in Patent Office2,450 DaysField of Search358/1.9, 358/1.2, 358/2.99, 358/3.01, 358/3.02, 358/3.06, 358/3.09, 358/3.1, 358/3.21, 358/3.26, 358/2.1, 358/463, 358/176, 358/209US Class Current358/3.01CPC Class CodesH04N 1/405 Halftoning, i.e. converting...
