Comparison of handwritings 3' Representation of Handwritten Images

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Comparison of handwritings3. Representation of
Handwritten Images

• Miroslava Boeková
• Thesis supervisor Doc. RNDr. Milan Ftácnik, PhD
• http//sprite.edi.fmph.uniba.sk/bozekova/

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Methods

• Bitmap Encoding
• Chain-code Encoding
• Fax-compressed Images
• Horizontal Run-length Encoding
• Block-adjacency Graph (BAG)
• Vertical Run-length Encoding
• Directional singly-connected chain (DSCC)

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Bitmap Encoding

• Is popular but any image manipulation is very
  slow.

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Chain-code Encoding I.

• Store only the information about the pixels on
  the boundary of black regions. The image is
  represented as a list of exterior and interior
  contours. Each contour is an array of
  consecutive boundary pixels, where each pixel is
  represented by its x and y coordinates, and some
  other derivable information such as the length
  and type of the contour, size of the bounding
  box, etc.

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Chain-code Encoding II.
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Fax-compressed Images

• Image is scanned row by row from left to right
  and the lengths of horizontal runs (horizontal
  line segments of pixels of the same color) of
  white pixels and the lengths of horizontal runs
  of black pixels are encoded using a Huffman code.

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Horizontal Run-length Encoding

• Is a straightforward modification of the fax
  representation. One simply keeps track of
  horizontal runs of black pixels, storing the
  coordinates of the first pixel and the run
  length. We also need to keep track of neighbor
  runs, i.e. runs above and below that touch the
  current run.

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Block-adjacency Graph (BAG) I.

• It is a generalization of the line-adjacency
  graph (LAG) where adjacent horizontal runs with
  the same starting and ending columns are merged
  into a block that is encoded by the coordinates
  of its top-left and bottom-right corners.

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Block-adjacency Graph (BAG) II.
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Vertical Run-length Encoding

• Is similar to the horizontal representation.

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Directional singly-connected chain (DSCC) I.

• horizontal or vertical - A horizontal DSCC
  consists of a black pixel run-length array
  R1,R2,,Rm, where Ri is a vertical run-length.
  Two neighboring run-lengths Ri and Ri1 are
  merged into a DSCC if they are singly connected
  in the horizontal direction.

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Directional singly-connected chain (DSCC) II.
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• A DSCC is a chain of run-lengths which are singly
  connected. A basic characteristic of a line is
  that it runs in only one direction. Run-lengths
  perpendicular to the direction of a line are
  merged into a DSCC. When a junction is
  encountered, the merging process stops and a new
  DSCC generates. Each DSCC represents a line
  segment, and multiple collinear DSCCs may be
  merged into a line, based on pre-defined rules.

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References

• TO DO