Method of compressing digital ink
First Claim
1. A method of compressing a digital ink input including a sequence of strokes input at an input device of a processing system, the method comprising the steps of, carried out by a processor of the processing system:
- representing each stroke input at the input device as a series of digital words representing x and y co-ordinates;
expressing at least one reference co-ordinate of each stroke in absolute terms; and
expressing a co-ordinate other than the at least one reference co-ordinate as an offset from a preceding co-ordinate,wherein the co-ordinate other than the at least one reference co-ordinate is represented as a combination of an estimate determined from the previous m co-ordinates and a residual error value, andthe estimate is calculated from the previous m co-ordinates using the formula;
where ci are coefficients selected to model characteristics of the digital ink, and α
represents either an x or a y co-ordinate.
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Abstract
A method of compressing a digital ink input including a sequence of strokes is provided in which each stroke is represented as a series of digital words representing x and y co-ordinates, at least one reference co-ordinate of each stroke is expressed in absolute terms, and a co-ordinate other than the at least one reference co-ordinate is expressed as an offset from a preceding co-ordinate. The co-ordinate other than the at least one reference co-ordinate is represented as a combination of an estimate determined from the previous m co-ordinates and a residual error value.
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Citations
13 Claims
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1. A method of compressing a digital ink input including a sequence of strokes input at an input device of a processing system, the method comprising the steps of, carried out by a processor of the processing system:
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representing each stroke input at the input device as a series of digital words representing x and y co-ordinates; expressing at least one reference co-ordinate of each stroke in absolute terms; and expressing a co-ordinate other than the at least one reference co-ordinate as an offset from a preceding co-ordinate, wherein the co-ordinate other than the at least one reference co-ordinate is represented as a combination of an estimate determined from the previous m co-ordinates and a residual error value, and the estimate is calculated from the previous m co-ordinates using the formula; where ci are coefficients selected to model characteristics of the digital ink, and α
represents either an x or a y co-ordinate.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
for y co-ordinates; C1=1.912 C2=−
0.913.
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9. A method as claimed in claim 1 wherein m is 3, and a given co-ordinate may be defined:
{tilde over (α
)}n=c1α
n−
1+c2α
n−
2+c3α
n−
3.
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10. A method as claimed in claim 9 wherein C1>
- 0 and C2<
0 and C3<
1.
- 0 and C2<
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11. A method as claimed in claim 9 or 10 wherein the coefficient values (Ci) for x co-ordinates are different to the coefficients for y co-ordinates.
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12. A method as claimed in claim 11 wherein for x co-ordinates:
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C1=1.799 C2=−
0.722C3=−
0.078, andfor y co-ordinates; C1=2.009 C2=−
1.107C3=−
0.098.
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13. A method as claimed in claim 1, further comprising the steps of discarding the estimate, and storing the residual error.
Specification