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

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

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