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Method and apparatus for drawing and erasing calligraphic ink objects on a display surface

  • US 9,207,858 B2
  • Filed: 10/14/2010
  • Issued: 12/08/2015
  • Est. Priority Date: 10/15/2009
  • Status: Active Grant
First Claim
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1. A method of generating a calligraphic ink object, comprising:

  • sampling contact coordinates generated by a coordinate input device during writing thereon using a pointer having a tip to generate an ink trajectory generally representing the writing;

    surrounding each sampled contact coordinate along the generated ink trajectory with a pointer tip instance, and for each consecutive pair of sampled contact coordinates, generating inner and outer line segments on opposite sides of a line segment joining the sampled contact coordinates of the pair, that extend between and are tangential to the peripheries of the pointer tip instances surrounding the sampled contact coordinates of the pair;

    generating an ink envelope between three successive contact coordinates, the ink envelope comprising an outer envelope formed by the outer line segments and an inner envelope formed by the inner line segments, wherein only the outer envelope includes envelope points on the pointer tip instance of a middle one of the three successive contact coordinates when the inner line segments intersect, and wherein the inner envelope includes an intersection point of the inner line segments as an envelope point in lieu of envelope point on the pointer tip instance of the middle one of the three successive contact coordinates;

    generating a smoothed ink envelope at least by fitting curves to points on said ink envelope; and

    drawing the smoothed ink envelope on a display surface thereby to generate the calligraphic ink object.

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