function coords_  = segmentation (image, coords)
  ## 'image' is a [height x width] matrix of floating point numbers
  ## between 0 (black) and 1 (white).

  ## 'coords' is a vector of x, y floating point coordinates in the
  ## image, corresponding to the currently selected region.

  ## 'coords_' should be a vector of x, y floating point coordinates in
  ## the image, corresponding to a step refinement of 'coords' towards
  ## the selection of an "homogeneous" region in the image.

  coords_ = coords;
endfunction
