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Ppmglobe User Manual(0) 						  Ppmglobe User Manual(0)

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 cylin-
       drical projection, it produces 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 cartographers show the three dimensional information in such a  two
       dimensional map.  The cylindrical projection is one.  You could make a cylindrical projec-
       tion by tracing as folows: 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 origi-
       nal 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 maps.jpl.nasa.gov <http://maps.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 number 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,  ppm-
       globe 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
       -background=colorname
	      This specifies the color that goes between the strips.

	      Specify the color (color) as described for the  argument	of  the  ppm_parsecolor()
	      library routine <libppm.html#colorname> .

	      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.   Some-
	      times,  it  is  impossible  to represent a named color exactly due to 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 situ-
	      ation.

	      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.

netpbm documentation			 23 February 2006		  Ppmglobe User Manual(0)
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