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Geometric Normalization of Hand-Written Characters

IP.com Disclosure Number: IPCOM000102250D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 6 page(s) / 191K

Publishing Venue

IBM

Related People

Narasimha, MS: AUTHOR [+2]

Abstract

This article describes a method of reducing, or normalizing, the size of hand-written characters. Key features of the method are that it does not change the aspect ratio of the character and that the number of black pels in the normalized character is selectable. The latter is used to advantage by forcing the percentage of black pels in the normalized character to be equal to the percentage of black pels in the unnormalized character. These features are especially important when the normalized characters are to be machine recognized.

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Geometric Normalization of Hand-Written Characters

       This article describes a method of reducing, or
normalizing, the size of hand-written characters.  Key features of
the method are that it does not change the aspect ratio of the
character and that the number of black pels in the normalized
character is selectable.  The latter is used to advantage by forcing
the percentage of black pels in the normalized character to be equal
to the percentage of black pels in the unnormalized character.  These
features are especially important when the normalized characters are
to be machine recognized.

      Proposed Normalization Method:

      Step 1 - Determine the Normalization Factors: The first step in
the normalization is to determine the normalization factors.  These
are defined as the ratio of the width (or depth) of the unnormalized
character to the width (or depth) of the normalized character.
                     CHARWIDTH-1
      NORMFACTORH =  -----------
                     NORMWIDTH
                     CHARDEPTH-1
      NORMFACTORV =  -----------
                     NORMDEPTH

      NORMFACTORH and NORMFACTORV are the normalization factors in
the horizontal and vertical directions. CHARWIDTH and CHARDEPTH are
the width and depth of the unnormalized character, while NORMWIDTH
and NORMDEPTH are the width and depth of the normalized character.

      Although it is possible to normalize a character differently in
the horizontal and vertical directions, doing so will change the
aspect ratio of the character, which may be undesirable.  To prevent
this distortion, one should select the larger of the two
normalization factors, and use this to normalize the character in
both directions.  This will cause the character to just fit the
normalized character box in one direction, while the other direction
may or may not reach the edges of the normalized character box.  The
overall normalization factor is therefore defined as:
      NORMFACTOR = MAX(NORMFACTORH, NORMFACTORV)

      An example of an unnormalized character is shown in Figure 1.
The character is overlayed with a grid which will be described later.

      This character is 45 pels wide and 49 pels deep.  If it is
desired to normalize this character to 15 pels by 15 pels, then the
horizontal and vertical normalization factors would be:
                     (45-1)
      NORMFACTORH =  ------- = 2.93
                       15
                     (49-1)
      NORMFACTORV =  ------- = 3.20
                       15 and the overall normalization factor is:
 NORMFACTOR =   MAX(2.93,3.20) = 3.20

      Step 2 - Define the Grid: The next step in the normalization is
to define the grid to be overlayed on the unnormalized character.
This grid will be centered...