RMotion
* RMotion provides a simple interface to build motion detection software in ruby.

Author
* Riccardo Cecolin
* rikiji at playkanji dot com
* http://www.rikiji.it

Documentation
* You need libopencv-dev, libhighgui-dev and libfftw3-dev to compile this extension.
* For usage examples check examples/first.rb and examples/second.rb
* http://www.rikiji.it/post/19
* http://www.rikiji.it/post/20

Require the lib, instantiate the main object and print default options:

irb(main):001:0> require 'rmotion'
=> true
irb(main):002:0> m=Motion.new
=> #<Motion:0xb74d14a0>
irb(main):003:0> m.show?
=> true
irb(main):004:0> m.write?
=> false
irb(main):005:0> m.fft?
=> true

http://www.youtube.com/watch?v=HNL-2pNkuSo&feature=player_embedded

show, write and fft are the most important options.	When show is true
 the video analyzed is also displayed in a window. You can set write 
to a string (a filename) to save the video analyzed to a file! Both 
displayed and saved video will have motion detection markings on it, 
like the video i just showed to you.

fft manages how the video frames are processed (fast fourier transform
 or direct): i recommend to set it always true, except in case your 
cpu isn't fast enough to follow the stream in realtime. Soon i'll 
post an in-depth analysis of what's the difference between fft=true
 and fft=false.

irb(main):006:0> m.fill?
=> true
irb(main):007:0> m.rect?
=> false
irb(main):008:0> m.point?
=> false

Next group of options is about output frames: fill default true behaves
 like the previous video, rect draws rectangles around moving objects
 and point draws instead a small circle centered on the object. Let's
 see them! Note that i can swap them live!

http://www.youtube.com/watch?v=0LQIt0XiWqE&feature=player_embedded

irb(main):012:0> m.threshold_fft?
=> 1.0
irb(main):013:0> m.threshold_direct?
=> 8.0
irb(main):014:0> m.threshold_distance?
=> 9.0
irb(main):015:0> m.threshold_group?
=> 20

threshold_fft and threshold_direct values influence what is recognized 
as noise and what as an object. Note that they are used in a mutually
 exclusive way: if fft is true then threshold_direct won't affect result.
 Same for fft as false and threshold_fft. Play with those value to fit
 your enviroment (light, object speed..).

threshold_distance and threshold_group also have a role on recognizing
 objects: an object is a group of al least group cells distant each other
 no more than distance. So you can choose min size of objects and spread
 of cells. Cells are a group of pixel determined dynamically on camera 
resolution, so don't worry about it.