\
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.TH "Pamshadedrelief User Manual" 0 "26 July 2014" "netpbm documentation"

.SH NAME

pamshadedrelief - generate shaded relief image from an elevation map

.UN synopsis
.SH SYNOPSIS

\fBpamshadedrelief\fP

[\fB-gamma\fP \fIg\fP]


.UN description
.SH DESCRIPTION
.PP
This program is part of
.BR "Netpbm" (1)\c
\&.
.PP
\fBpamshadedrelief\fP 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.
.PP
The image \fBpamshadedrelief\fP creates is as if illumated by a light
source from the left.
.PP
The output image is a PAM with tuple type \fBGRAYSCALE\fP.
.PP
The program \fBpamcrater\fP is a good thing to use to demonstrate the
function of \fBpamshadedrelief\fP.  It generates a terrain map of a cratered
landscape.

.nf
\f(CW
    $ pamcrater | pamshadedrelief | pamx
\fP  
.fi


.UN options
.SH OPTIONS
.PP
All options can be abbreviated to their shortest unique prefix.


.TP
\fB-gamma\fP \fIfactor\fP
The specified \fIfactor\fP is used to gamma adjust the image in
the same manner as performed by \fBpnmgamma\fP.  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.
.sp
Note that this is separate from the gamma correction that is part of the
definition of the PAM GRAYSCALE format.  The image \fBpamshadedrelief\fP
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.



.UN designnotes
.SH DESIGN NOTES

The\fB-gamma\fP option isn't really necessary since you can achieve
the same effect by piping the output from \fBpamshadedrelief\fP through
\fBpnmgamma\fP.  However, \fBpamshadedrelief\fP 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.


.UN seealso
.SH SEE ALSO
.BR "ppmrelief" (1)\c
\&
.BR "pnmgamma" (1)\c
\&,
.BR "pnmsmooth" (1)\c
\&
.BR "pamcrater" (1)\c
\&
.BR "pam" (5)\c
\&,


.SH AUTHOR
.PP
\fBpgmcrater\fP, from which this is derived, was written by John Walker:

.nf
John Walker
Autodesk SA
Avenue des Champs-Montants 14b
CH-2074 MARIN
Suisse/Schweiz/Svizzera/Svizra/Switzerland
    \fBUsenet:\fP\fIkelvin@Autodesk.com\fP
    \fBFax:\fP038/33 88 15
    \fBVoice:\fP038/33 76 33
.fi
.PP
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.


.UN history
.SH HISTORY
.PP
\fBpgmcrater\fP was split into \fBpamshadedrelief\fP and \fBpamcrater\fP
in Netpbm 10.68 (September 2014).  See the history section of the
\fBpamcrater\fP manual for details.
.SH DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source.  The master documentation is at
.IP
.B http://netpbm.sourceforge.net/doc/pamshadedrelief.html
.PP