plucky (1) ppmglobe.1.gz

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 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 ⟨http://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  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