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 .)

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)