Dynamic Glyph Generation

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Dynamic Glyph Generation

• Based on variable length encoding schema

Yap Cheah Shen eForth Technology. Glyph
Typesetting Workshop Kyoto, 29Nov2003
2
Outline of Presentation

• Morpheme Latin vs. Han
• Latin text encoding
• Missing character in Chinese text
• Solution
• Implementation details
• Glyph decomposition database
• Topological conversion of strokes
• Automatic frame calculation
• Integrating to existing OS
• Other issue

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Morpheme Latin vs. Han

• Morpheme is the smallest meaningful unit in a
  language.
• For Latin text, it is word.
• For Chinese text, it is Hanzi or Kanji.
• Representing a real-world idea, morpheme keeps
  changing from time to time
• Morphemes form an open-set.

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Latin Text Encoding

• Alphabets form a fix set of symbols.
• All words can be represented as sequences of
  alphabets.
• They are the ideal encoding units for Latin text
  e.g., ASCII.
• No missing word encoding problem.

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Missing Characters in Chinese Text

• Not all existing Hanzi are encoded.
• Hanzi are in an open-set , theoretically,
  historically and practically.
• Wrong assumptions and designs of existing
  encoding schema.
• Unending loop of assigning code point, OS update,
  new font, new input method table Industries are
  happy. (users suffer)

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Solution-1

• Parts or components as encoding unit.
• ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
• Most characters can be represented by a finite
  set of basic parts.
• Strokes are used to construct rarely used parts.(
  thousand of parts appear only once or twice)

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Solution -2

• A close-set of basic parts and strokes as
  encoding unit.
• 3 Joining operator horizontal , vertical, and
  enclosing.
• 1 Shielding operator for hiding stroke
• Prefix notation allowing recursive composition.

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Solution-3

• Ordinary CJK fix-length encoding schema, numeric
  value as character code.
• Input method table
• Convert input keystroke to character code.
• Static Font file
• Glyph data is pre-designed
• Access glyph data by character code.
• Text file
• Sequence of character code.

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Solution-4

• Additional feature of variable length encoding
  CJK environment.
• Input
• Character can be sorted, filtered by parts.
• Compatible with any existing input method.
• Display
• Font file stores commonly used characters and
  parts.
• Generate glyph on the fly by glyph descriptive
  sequence.
• Storage and data-exchange
• Compatible with Unicode.
• Ideographic description sequence.

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Dynamic Glyph Generator

• Input
• Various type of Variable length descriptive
  character code sequence.
• ??? of Academia Sinica
• ??? of CBETA
• Unicode ideographic descriptive characters
• Output display print
• True-type compatible outline
• Rasterized bitmap.
• Macromedia Flash, SVG
• The Task a layout problem, fitting a 1
  dimensional sequence into a 2 dimensional square.

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Implementation -1

• The system consists of 3 major parts
• Glyph decomposition database
• Courtesy of Prof. Hsieh from Academia Sinica,
  Taiwan http//www.sinica.edu.tw/cdp/
• Outline of strokes and components
• Beijing ZhongYi Co. professional outline font
  vendor. http//www.zhongyicts.com.cn/
• The eForth system putting everything together,
  hardware-software co-engineering.

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Implementation-2

• Glyph decomposition database
• All CJK glyph defined by Unicode 4.0 , 71000 in
  total.
• 549 basic parts, stroke sequence are preserved
• 3996 total parts
• Total parts frequency 165122
• Accumulated frequency
• Top 50 51389 31
• Top 200 87381 53
• Top 1000 129393 78

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Implementation-3

• Stroke are describe as a outline with skeletal
  line.
• Both outline and skeletal line are Quadric Bezier
  curves.
• Outline points are recalculated according to
  scaled- skeletal line.
• Result
• Stroke data is highly reusable
• Stroke weights are adjustable

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Implementation-4

• Automatic frame calculation
• Algorithm of estimating the complexity of each
  parts, to decide the proportion of the part in
  result glyph.
• ? ?25, ? 70 , roughly.
• ? ? 55, ? 40, roughly.
• Result
• Clear glyph descriptive expressions
• Search engine friendly
• Human readable

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Integrating into existing OS/GUI

• String manipulation library
• Number of characters
• -1 for operators, 1 for characters
• Characters width
• Graphic sub-system
• drawing a text line (e.g. ExtTextOut)
• Text handling widgets
• Awareness of glyphs expression for caret,
  selection and delete/backspace.

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Other Issues

• Quality of the glyph
• Trade-off with space More part outlines, better
  quality.
• Speed of generation
• No problem for IBM PC, glyph generation is rare.
• For handheld device, Hardware acceleration is
  recommended.

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Examples

• ? Vertical combination
• ? Horizontal combination
• ? enclosing
• hide
• ? ??? or ?????
• ??? ?-5 hide 5th stroke
• ?? ?-5
• ?-4 U20009

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Thank You