Electronic high-fidelity screenless conversion system and method using a separable filter
First Claim
1. A system for converting one input value of a series of input values into an output value wherein previous input values have been converted to previous output values and subsequent input values are to be converted to output values, the system comprising:
- error generating means for generating first and second errors for the one input value undergoing conversion, wherein the first error is based upon application of a one dimensional separable filter to a selected number of previous output values, to output values predicted for a certain number of subsequent input values, and to an output value having an assumed first level for the one input value undergoing conversion, and wherein the second error is based upon application of the one dimensional separable filter applied to the selected number of previous output values, to the output values predicted for the certain number of subsequent input values, and to an output value having an assumed second level for the one input value undergoing conversion; and
output value setting means for setting the one input value undergoing conversion to an output value having the first level if the first error is less than the second error and to an output value having the second level if the first error is greater than the second error.
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Abstract
A system for converting a continuous tone value to an output value having either a first level or a second level develops a first error based upon the application of a separable filter to an output value having a first level assumed for the continuous tone value undergoing conversion. A second error is developed based upon the application of the separable filter to an output value having a second level assumed for the continuous tone value undergoing conversion. If the first error is greater than the second error, the continuous tone value is converted to the output value having the second level. Otherwise, the continuous tone value is converted to the output value having the first level. The resulting error is diffused in a predetermined manner to neighboring continuous tone values yet to be converted.
33 Citations
38 Claims
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1. A system for converting one input value of a series of input values into an output value wherein previous input values have been converted to previous output values and subsequent input values are to be converted to output values, the system comprising:
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error generating means for generating first and second errors for the one input value undergoing conversion, wherein the first error is based upon application of a one dimensional separable filter to a selected number of previous output values, to output values predicted for a certain number of subsequent input values, and to an output value having an assumed first level for the one input value undergoing conversion, and wherein the second error is based upon application of the one dimensional separable filter applied to the selected number of previous output values, to the output values predicted for the certain number of subsequent input values, and to an output value having an assumed second level for the one input value undergoing conversion; and output value setting means for setting the one input value undergoing conversion to an output value having the first level if the first error is less than the second error and to an output value having the second level if the first error is greater than the second error. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for sequentially converting input values into corresponding output values so that, at a given instant in time, an input value undergoing conversion has before it input values previously converted to corresponding output values and after it subsequent input values yet to be converted to output values, the system comprising:
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a separable filter; error generating means for generating first and second errors for the input value undergoing conversion;
the first error being based upon application of the separable filter to a two dimensional array comprising a first set of output values corresponding to the previously converted input values, a second set of output values corresponding to the subsequent input values and an output value having a first level assumed for the input value undergoing conversion and the second error being based upon application of the separable filter to a further two dimensional array comprising the first and second sets of output values and an output value having a second level assumed for the input value undergoing conversion; andoutput value setting means for setting the input value undergoing conversion to the output value having the first level if the first error is less than the second error and to the output value having the second level if the first error is greater than the second error. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of converting input values to corresponding output values wherein an input value undergoing conversion has before it previously converted input values and after it input values yet to be converted and wherein each of the input values has one of at least M possible levels and each of the output values has one of N possible levels where M is greater than N, the method comprising the steps of:
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(a) using a separable filter to generate N errors wherein each of the N errors is based upon an output value having a corresponding one of the N possible levels assumed for the input value undergoing conversion and wherein at least one of the N errors is smallest;
(b) converting the input value undergoing conversion to an output value having a level associated with the smallest error;(c) diffusing the smallest error to a predetermined number of input values yet to be converted; and (d) repeating steps (a)-(c) for each of the input values yet to converted. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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Specification