man > pgmdeshadow(1)

Pgmdeshadow User Manual(1)             General Commands Manual            Pgmdeshadow User Manual(1)

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 recon‐
       struction 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, "Morpho‐
       logical Grayscale Reruction in Image Analysis: Applications and Efficient Algorithms.



OPTIONS
       There are no command line options defined specifically for pgmdeshadow, but it recognizes the
       options common to all programs based on libnetpbm (See ]8;;index.html#commonoptions\ Common Options]8;;\ .)


REFERENCES
       •      Luc Vincent, "Morphological Grayscale Reconstruction in Image  Analysis:  Applications
              and Efficient Algorithms," 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).

DOCUMENT SOURCE
       This  manual  page  was  generated by the Netpbm tool 'makeman' from HTML source.  The master
       documentation is at

              http://netpbm.sourceforge.net/doc/pgmdeshadow.html

netpbm documentation                        06 July 2006                  Pgmdeshadow User Manual(1)