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 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 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,
       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  ⟨index.html#commonoptions⟩  ), ppmglobe 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 ⟨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.

       -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