MapStitch - merge multiple 2D maps
=================================

 This is a ROS component and a command line tool to align a map to a previously
saved 2D map. The previously saved map is assumed to have been created by the
map_saver ROS component. The implementation is based on opencvs
estimateRigidTransform function, ORB feature extraction and matching the
distance of pairwise feature candidates.

ROS component
=============

 The ROS component can be run with "rosrun mapstitch ros_mapstitch" and supports
three parameters:
 * max_distance, the treshold distance for filtering pairwise distances. Too
   high does not filter any features and too low filter too much. This is the
   pixel distance between matches in both maps, so should be set depending on
   the resolution of your maps.
 * debug, set to true will save the current_stitch.pgm and current_map.pgm, i.e.
   the stitchted maps and the current map as seen on /map.

 The component will listen on the /world topic for the OccupancyGrid-Map to
align the /map topic one to. At the moment no scaling is implemented, so the
maps need to have the same resolution. The transformation from /map to /world
will be published on the frame_ids given in the /map and /world topics.

 The node now listen to three topics:
  /map    - publish the /map->/world (frame_ids) transform on update
  /world  - receive the world map on this latched topic
  /align  - receive the map used for alignment

 We have three topics to be able to publish two "complete" maps on /align and 
/world and calculate a "static" transform and then publish this transform 
whenever something on /map keeps published (this is needed so the transform 
does not timeout).

Command Line Tool
=================

 The command line tool can be run with bin/mapstitch and can be used to align
two previosuly saved .pgm maps on each other. It is mainly meant for testing and
debugging. The Usage is

bin/mapstitch  [-o <string>] [-v] [-d <max-distance>] [--] [--version]
                  [-h] <file1 and file2> ...


Where:

   -o <string>,  --outfile <string>
     output filename

   -v,  --verbose
     verbose output

   -d <max-distance>,  --maximum-distance <max-distance>
     maximum distance on matched points pairs for inclusion

   --,  --ignore_rest
     Ignores the rest of the labeled arguments following this flag.

   --version
     Displays version information and exits.

   -h,  --help
     Displays usage information and exits.

   <file1 and file2>  (accepted multiple times)
     input file names (first one is pivot element)


   Aligns multiple scan maps and combines into a single image. All images
   given on the command line will be aligned to the first supplied image
   and their respective rotation/translation and transformation matrix will
   be returned.



TODO
----
 * check that world file and /map have the same resolution