pixels are considered outliers, be
 careful not to set too low. [minArea] determines coarsest scale beyond
 which the image is not downsampled (should not be set too low). [H0] can
 be used to specify an initial alignment. Use [show] to display results.

 USAGE
  [H,Ip] = imagesAlign( I, Iref, varargin )

 INPUTS
  I          - transformed version of I
  Iref       - reference grayscale double image
  varargin   - additional params (struct or name/value pairs)
   .type       - ['projective'] see