NAME

       pamshadedrelief - generate shaded relief image from an elevation map

SYNOPSIS

       pamshadedrelief

       [-gamma g]

DESCRIPTION

       This program is part of Netpbm(1).

       pamshadedrelief  creates  a  shaded  relief  image from an elevation map.  A shaded relief
       image is a visual image of terrain, showing the terrain as if illuminated by oblique light
       and  viewed  from  above,  so  that  the brightess of each spot depends upon its slope.  A
       common example of a shaded relief image  is  a  relief  map  of  the  Earth,  which  shows
       mountains and valleys.

       The image pamshadedrelief creates is as if illumated by a light source from the left.

       The output image is a PAM with tuple type GRAYSCALE.

       The   program   pamcrater  is  a  good  thing  to  use  to  demonstrate  the  function  of
       pamshadedrelief.  It generates a terrain map of a cratered landscape.

           $ pamcrater | pamshadedrelief | pamx

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common  Options  ⟨index.html#commonoptions⟩  ),  pamshadedrelief recognizes the following
       command line option:

       -gamma factor

       -g factor
              The specified factor is used to gamma adjust  the  image  in  the  same  manner  as
              performed  by  pnmgamma.   The  default  value  is  1.0,  which results in a medium
              contrast image.  Values larger than 1 lighten the image and reduce contrast,  while
              values less than 1 darken the image, increasing contrast.

              Note that this is separate from the gamma correction that is part of the definition
              of the PAM GRAYSCALE format.  The image pamshadedrelief  generates  is  a  genuine,
              gamma-corrected  PAM  GRAYSCALE  image in any case.  This option simply changes the
              contrast and may compensate for a display device that does not correctly render PAM
              GRAYSCALE images.

DESIGN NOTES

       The-gamma  option  isn't  really necessary since you can achieve the same effect by piping
       the output from pamshadedrelief through pnmgamma.  However,  pamshadedrelief  performs  an
       internal  gamma  map  anyway  in the process of rendering the elevation array into the PAM
       GRAYSCALE format, so there's no  additional  overhead  in  allowing  an  additional  gamma
       adjustment.

SEE ALSO

       ppmrelief(1) pnmgamma(1), pnmsmooth(1) pamcrater(1) pam(1),

AUTHOR

       pgmcrater, from which this is derived, was written by John Walker:

       John Walker
       Autodesk SA
       Avenue des Champs-Montants 14b
       CH-2074 MARIN
       Suisse/Schweiz/Svizzera/Svizra/Switzerland
           Usenet:kelvin@Autodesk.com
           Fax:038/33 88 15
           Voice:038/33 76 33

       Permission  to  use,  copy, modify, and distribute this software and its documentation for
       any purpose and without fee is hereby granted, without  any  conditions  or  restrictions.
       This software is provided "as is" without express or implied warranty.

HISTORY

       pgmcrater  was  split into pamshadedrelief and pamcrater in Netpbm 10.68 (September 2014).
       See the history section of the pamcrater manual for details.

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/pamshadedrelief.html