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

       ppmglobe	- generate strips to glue onto a sphere

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

       Minimum	unique abbreviation of option is acceptable.  You may use dou-
       ble 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.

       This program is part of Netpbm(1).

       ppmglobe	does the inverse of a  cylindrical  projection	of  a  sphere.
       Starting	 with  a  cylindrical 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	projection 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 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
       <> .

       stripcount  is the number of strips ppmglobe is to generate in the out-
       put.  More strips makes it easier to fit	onto a sphere  (less  stretch-
       ing,  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, ppmglobe produces a fractional strip on the right.

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

	      This specifies the color that goes between the strips.

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

	      The default is black.

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

	      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 im-
	      age'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).

       ppm(5) pnmmercator(1)

       ppmglobe	was new	in Netpbm 10.16	(June 2003).

       It is derived from Max Gensthaler's ppmglobemap.

       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.

       This  manual  page was generated	by the Netpbm tool 'makeman' from HTML
       source.	The master documentation is at

netpbm documentation	       23 February 2006	       Ppmglobe	User Manual(0)


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