Compression of digital ink
AssigneeMotorola, Inc.
InventorManjirnath Chatterjee
Life of this patent
Estimating the term…
Abstract
Compression of digital ink is achieved by calculating second order differences between consecutive elements in the digital ink and applying the differences to a Huffman encoder to produce a compressed bitstream. For digital ink that is not highly correlated, compression may be achieved by representing segments of the digital ink by mathematical shapes such as a Bezier curve or orthogonal elements and transmitting the shape instead of the digital ink.
Claims26
A method for lossless compression of digital ink, comprising the steps of:
- (a) subdividing digital ink comprising a plurality of digital ink strokes into digital ink points comprising coordinates;
- (b) separating the digital ink points comprising coordinates into separate coordinate arrays comprising array elements;
- (c) computing second order differences between consecutive array elements in each coordinate array;
- and
- (d) applying the second order differences to a Huffman encoder to generate a compressed bitstream.
A method for lossless decompression of digital ink, comprising the steps of:
- (a) applying a compressed bitstream to a Huffman decoder to generate second order differences;
- (b) computing consecutive array elements from the second order differences;
- (c) combining array elements to form digital ink points;
- and
- (d) joining the digital ink points to form digital ink comprising a plurality of digital ink strokes.
A method for lossless compression of digital ink, comprising the steps of:
- (a) separating each stroke in the digital ink into digital ink points;
- (b) separating each digital ink point into X-axis and Y-axis elements;
- (c) collating each X-axis element into an X-axis array and collating each Y-axis element into a Y-axis array;
- (d) calculating the maximum number of bits to represent the first two elements in the X-axis and Y-axis arrays, respectively;
- (e) calculating second order differences for each remaining element in the X-axis and Y-axis arrays, respectively;
- and
- (f) applying the second order differences to a Huffman encoder to generate a compressed bitstream.
A method for lossless decompression of digital ink, comprising the steps of:
- (a) applying a compressed bitstream to a Huffman decoder to generate second order differences;
- (b) calculating X-axis and Y-axis array elements for X-axis and Y-axis arrays, respectively;
- (c) separating X-axis and Y-axis elements into X-axis and Y-axis arrays, respectively;
- (d) combining X-axis and Y-axis elements into digital ink points;
- and
- (e) combining digital ink points into digital ink strokes.
A device for compression of digital ink, comprising:
- (a) a display interface comprising capture means for retrieving digital ink;
- (b) an analog to digital converter that translates captured digital ink into digital ink points comprising coordinates;
- (c) a digital processor which separates the coordinates into coordinate arrays
- (d) a difference analyzer to compute the offset between coordinates in each coordinate array to produce second order differences;
- and
- (e) a Huffman encoder generating a histogram of occurrences of the second order differences to produce an encoded bitstream.
The device of 19 further includes a bitstream processor that encapsulates the encoded bitstream into a data packet for transmitting to a remote computer.
A device for decompression of digital ink, comprising:
- (a) a Huffman decoder which takes an encoded bitstream to produce a histogram of occurrences of second order differences;
- (b) a summation analyzer to compute coordinates from the second order differences;
- (c) a digital processor to form digital ink comprising coordinates;
- (d) a digital to analog converter that translates digital ink comprising coordinates into digital ink points;
- and
- (e) a display interface comprising means for presenting the digital ink points on a display.
The device of 23 further includes a bitstream processor that retrieves an encoded bitstream with compressed digital ink from a remote computer.
Dependencies are inferred from the claim text.