pamshadedrelief - generate shaded relief image from an elevation map

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.comFax: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.

       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

       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.

       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

netpbm documentation                              26 July 2014                    PamshadedreliefUserManual(1)

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

       pamshadedrelief - generate shaded relief image from an elevation map

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

       -gammafactor-gfactor
              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.

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

pamshadedrelief

       [-gammag]