Feature extraction for real-time pattern recognition using single curve per pattern analysis
First Claim
Patent Images
1. A computer-implemented method comprising:
- recording coordinate values representing a two-dimensional pattern as a three-dimensional pattern, including storing x-coordinate and y-coordinate values in conjunction with a z-coordinate, the z-coordinate having a first value at times when the pattern is being entered and a second value at times when the pattern is not being entered;
fitting the x-coordinate, y-coordinate and z-coordinate values at sample points to a plurality of related mathematical basis functions by transforming the coordinate values at the sample points into coefficients of the function;
featurizing the input pattern into a plurality of features, at least some of the features corresponding to the coefficients of the basis function; and
performing computerized recognition by using the features to determine an alphanumeric value corresponding to the input pattern.
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Abstract
A feature extractor samples points on an input pattern drawn in real time. In addition to X and Y coordinates, each sample has an up/down or Z coordinate value representing whether or not the sample point is a perceptible part of the pattern. The groups of coordinate values are transformed into respective sets of coefficients of Chebyshev polynomials by least-squares fit. A recognition unit can use the coefficients as features to identify the character. Additional features, such as aspect ratio and center of gravity, are also derived to aid in recognizing the pattern or reconstructing its image.
90 Citations
32 Claims
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1. A computer-implemented method comprising:
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recording coordinate values representing a two-dimensional pattern as a three-dimensional pattern, including storing x-coordinate and y-coordinate values in conjunction with a z-coordinate, the z-coordinate having a first value at times when the pattern is being entered and a second value at times when the pattern is not being entered;
fitting the x-coordinate, y-coordinate and z-coordinate values at sample points to a plurality of related mathematical basis functions by transforming the coordinate values at the sample points into coefficients of the function;
featurizing the input pattern into a plurality of features, at least some of the features corresponding to the coefficients of the basis function; and
performing computerized recognition by using the features to determine an alphanumeric value corresponding to the input pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for recognizing an input pattern, comprising:
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sampling the input pattern so as to produce a plurality of groups of coordinate values, each of the groups including an up/down coordinate such that the plurality of groups represent the input pattern as a single curve independent of a number of strokes that formed the pattern;
transforming the groups of coordinate values into coefficients of a plurality of related mathematical basis functions; and
providing the coefficients as features to a feature-based recognizer, the recognizer using the features to return information that identifies the entire input pattern as belonging to one class of a set of possible classes. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for recognizing a two-dimensional input pattern corresponding to a plurality of separate pattern strokes, each stroke being entered during a pen-down condition that occurs between pen-up conditions, the method comprising:
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converting the input pattern into a single curve independent of pattern strokes by sampling the input pattern into a single set of a plurality of x-coordinate, y-coordinate and z-coordinate values, the z-coordinates having a first value corresponding to a pen-down condition or a second value corresponding to a pen-up condition;
transforming the x-coordinate, y-coordinate and z-coordinate values into coefficients of a plurality of related mathematical basis functions;
maintaining the coefficients, including those for the values representing the z-coordinate, as features of the input pattern; and
identifying the entire input pattern as belonging to one of a number of classes based on the features. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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28. A system for recognizing an input pattern, comprising:
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an input device for producing a plurality of signals corresponding to coordinates of the input pattern on the input device, at least one of the signals identifying an up/down state of input, the coordinates representing the input pattern as a single curve independent of a number of pattern strokes that form the input pattern;
a data processor for transforming the signals into coefficients of related basis functions; and
a recognition unit responsive to the coefficients for identifying the input pattern as belonging to one of a number of classes. - View Dependent Claims (29, 30, 31)
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32. A computer-readable medium having computer-executable instructions, which when executed perform a method, comprising:
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sampling an input pattern comprising a plurality of distinct strokes, so as to produce a plurality of coordinate values including values representing an up/down coordinate, the plurality of coordinate values representing the input pattern as a single curve independent of how many distinct pattern strokes are in the plurality;
transforming the coordinate values, including those for the values representing the up/down coordinate, into coefficients of a set of basis functions;
maintaining the coefficients as features of the input pattern; and
identifying the input pattern as belonging to one of a number of classes based on the features.
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Specification