Manual: ppmglobe

Ppmglobe User Manual(1)				   General Commands Manual			     Ppmglobe User Manual(1)

NAME
       ppmglobe - generate strips to glue onto a sphere

SYNOPSIS
       ppmglobe [-background=colorname] [-closeok] stripcount [filename]

       Minimum	unique	abbreviation of option is acceptable.  You may use double hyphens instead of single hyphen to denote
       options.	 You may use white space in place of the equals sign to separate an option name from its value.

DESCRIPTION
       This program is part of Netpbm(1).

       ppmglobe does the inverse of a cylindrical projection of a sphere.  Starting with a cylindrical projection,  it	pro‐
       duces  an  image	 you  can cut up and glue onto a sphere to obtain the spherical image of which it is the cylindrical
       projection.

       What is a cylindrical projection?  Imagine a map of the Earth on flat paper.  There are lots of different  ways	car‐
       tographers  show the three dimensional information in such a two dimensional map.  The cylindrical projection is one.
       You could make a cylindrical projection by tracing as follows: wrap a rectangular sheet of paper	 around	 the  globe,
       touching	 the globe at the Equator.  For each point of color on the globe, run a horizontal line from the axis of the
       globe through that point and out to the paper.  Mark the same color on the paper there.	Lay the paper out  flat	 and
       you have a cylindrical projection.

       Here's  where  ppmglobe	comes  in:   Pass the image on that paper through ppmglobe and what comes out the other side
       looks something like this:

       Example of map of the earth run through ppmglobe

       You could cut out the strips and glue it onto a sphere and you'd have a copy of the original globe.

       Note that cylindrical projections are not what you normally see as maps of the Earth.  You're more likely  to  see  a
       Mercator	 projection.   In  the Mercator projection, the Earth gets stretched North-South as well as East-West as you
       move away from the Equator.  It was invented for use in navigation, because you can draw straight compass courses  on
       it, but is used today because it is pretty.

       You can find maps of planets at space.jpl.nasa.gov .

PARAMETERS
       stripcount  is the number of strips ppmglobe is to generate in the output.  More strips makes it easier to fit onto a
       sphere (less stretching, tearing, and crumpling of paper), but makes you do more cutting out of the strips.

       The strips are all the same width.  If the number of columns of pixels in the image doesn't evenly divide by the num‐
       ber of strips, ppmglobe truncates the image on the right to create nothing but whole  strips.   In  the	pathological
       case that there are fewer columns of pixels than the number of strips you asked for, ppmglobe fails.

       Before  Netpbm  10.32  (February	 2006), instead of truncating the image on the right, ppmglobe produces a fractional
       strip on the right.

       filename is the name of the input file.	If you don't specify this, ppmglobe reads the image from Standard Input.

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

       -background=colorname
	      This specifies the color that goes between the strips.

	      Specify the color (color) as described for the argument of the pnm_parsecolor() library routine .

	      The default is black.

	      This option was new in Netpbm 10.31 (December 2005).  Before that, the background is always black.

       -closeok
	      This means it is OK if the background isn't exactly the color you specify.  Sometimes,  it  is  impossible  to
	      represent	 a  named  color  exactly because of the precision (i.e. maxval) of the image's color space.  If you
	      specify -closeok and ppmglobe can't represent the color you name exactly, it  will  use  instead	the  closest
	      color to it that is possible.  If you don't specify closeok, ppmglobe fails in that situation.

	      This option was new in Netpbm 10.31 (December 2005).

SEE ALSO
       ppm(1) pnmmercator(1)

HISTORY
       ppmglobe was new in Netpbm 10.16 (June 2003).

       It is derived from Max Gensthaler's ppmglobemap.

AUTHORS
       Max  Gensthaler	wrote  a program he called ppmglobemap in June 2003 and suggested it for inclusion in Netpbm.  Bryan
       Henderson modified the code slightly and included it in Netpbm as ppmglobe.

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/ppmglobe.html

netpbm documentation				      23 February 2006				     Ppmglobe User Manual(1)