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Pgmdeshadow User Manual(0)                          Pgmdeshadow User Manual(0)



NAME
       pgmdeshadow - Deshadow a PGM image


SYNOPSIS
       pgmdeshadow

       [pnmfile]



DESCRIPTION
       This program is part of Netpbm(1).

       pgmdeshadow removes gray shadows from an image.  This is useful for an image containing text, such as a scanned
       book pages, where a shadow typically appears near the book crease or near one side of the  image.   pgmdeshadow
       recognizes  a  gray  shadow  as an area of smoothly changing color, starting from the outer edges of the image.
       The program uses a simple image reconstruction algorithm to determine the local shadow gray level, then divides
       each pixel's gray level by the local shadow gray level.

       The  algorithm  is  the  'fast hybrid grayscale reruction' algorithm from Luc Vincent, "Morphological Grayscale
       Reruction in Image Analysis: Applications and Efficient Algorithms.



OPTIONS
       None.


REFERENCES
       ?      Luc Vincent, 'Morphological Grayscale Reruction in Image  Analysis:  Applications  and  Efficient  Algo-
              rithms,' IEEE Transactions on Image Processing, vol. 2, no. 2, April 1993, pp. 176-201.





SEE ALSO
       ppmshadow(1), pgm(1)


HISTORY
       pgmdeshadow was added to Netpbm in Version 10.35 (August 2006).



netpbm documentation             06 July 2006       Pgmdeshadow User Manual(0)