pamshadedrelief - generate shaded relief image from an elevation map
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
All options can be abbreviated to their shortest unique prefix.
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.
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.
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.