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

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

35       None.
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REFERENCES

39       ·      Luc Vincent, 'Morphological Grayscale Reruction in Image  Analy‐
40              sis:  Applications  and Efficient Algorithms,' IEEE Transactions
41              on Image Processing, vol. 2, no. 2, April 1993, pp. 176-201.
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SEE ALSO

48       ppmshadow(1), pgm(1)
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HISTORY

52       pgmdeshadow was added to Netpbm in Version 10.35 (August 2006).
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56netpbm documentation             06 July 2006       Pgmdeshadow User Manual(0)