NAME:
  colcob
 PURPOSE:
  Compute the offset from the center-of-light to center-of-body.
 DESCRIPTION:

 CATEGORY:
  Miscellaneous
 CALLING SEQUENCE:
  colcob,map,npix,radius,pole,selat,selon,sslat,sslon,dx,dy
 INPUTS:
  map    - Array containing a full map of surface, see RENDER.PRO for a
               more complete description of what's needed here.
  npix   - size of the array for the computation (pixels), the image used
               for the computation is square and the object just fits in
               the array.
  radius - Radius of object in km.
  pole   - Position angle of pole, east from north (degrees)
  selat  - Sub-earth latitude (degrees)
  selon  - Sub-earth longitude (degrees)
  sslat  - Sub-solar latitude (degrees)  Only used for Hapke functions. 
  sslon  - Sub-solar longitude (degrees)  Only used for Hapke functions.

 OPTIONAL INPUT PARAMETERS:

 KEYWORD INPUT PARAMETERS:
  Accepts all keywords supported by RENDER.PRO.  Many of these are needed
    to support the proper calculation of the surface reflectance.

 OUTPUTS:
  dx     - X position of the center-of-light in km (actually this is just
               in the same units as radius but generally should be km).
  dy     - Y position of the center-of-light.
 KEYWORD OUTPUT PARAMETERS:
  IMAGE  - Rendered image computed for calculation.
  FLUX   - Total flux (I/F) of the rendered image.

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
  1998/02/17, Written by Marc W. Buie, Lowell Observatory
  2009/02/01, MWB, nearly a total rewrite both in documentation, coding, and
                 operation.  This new version is NOT compatible with the old.