1Pgmdeshadow User Manual(0)                          Pgmdeshadow User Manual(0)
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NAME

6       pgmdeshadow - Deshadow a PGM image
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SYNOPSIS

10       pgmdeshadow
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12       [pnmfile]
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DESCRIPTION

16       This program is part of Netpbm(1).
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18       pgmdeshadow  removes gray shadows from an image.  This is useful for an
19       image containing text, such as a scanned book  pages,  where  a  shadow
20       typically  appears  near the book crease or near one side of the image.
21       pgmdeshadow recognizes a gray shadow as an area  of  smoothly  changing
22       color,  starting from the outer edges of the image.  The program uses a
23       simple image reconstruction algorithm to  determine  the  local  shadow
24       gray  level,  then  divides each pixel's gray level by the local shadow
25       gray level.
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27       The algorithm is the "fast hybrid grayscale reruction"  algorithm  from
28       Luc  Vincent,  "Morphological  Grayscale  Reruction  in Image Analysis:
29       Applications and Efficient Algorithms.
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OPTIONS

34       There are no command line options defined specifically for pgmdeshadow,
35       but it recognizes the options common to all programs based on libnetpbm
36       (See
37        Common Options ⟨index.html#commonoptions⟩ .)
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REFERENCES

41       ·      Luc Vincent, "Morphological Grayscale  Reconstruction  in  Image
42              Analysis:  Applications and Efficient Algorithms," IEEE Transac‐
43              tions on Image Processing,  vol.  2,  no.  2,  April  1993,  pp.
44              176-201.
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SEE ALSO

51       ppmshadow(1), pgm(1)
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HISTORY

55       pgmdeshadow was added to Netpbm in Version 10.35 (August 2006).
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DOCUMENT SOURCE

58       This  manual  page was generated by the Netpbm tool 'makeman' from HTML
59       source.  The master documentation is at
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61              http://netpbm.sourceforge.net/doc/pgmdeshadow.html
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63netpbm documentation             06 July 2006       Pgmdeshadow User Manual(0)
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