__all__ = ['otsu_segmentation']

def otsu_segmentation(image, k, mask=None):

    """

    Otsu image segmentation

    This is a very fast segmentation algorithm good for quick explortation, 

    but does not return probability maps.

    ANTsR function: `thresholdImage(image, 'Otsu', k)`

    Arguments

    ---------

    image : ANTsImage 

        input image

    k : integer

        integer number of classes. Note that a background class will 

        be added to this, so the resulting segmentation will 

        have k+1 unique values.

    mask : ANTsImage 

        segment inside this mask

    Returns

    -------

    ANTsImage

    Example

    -------

    >>> import ants

    >>> mni = ants.image_read(ants.get_data('mni'))

    >>> seg = mni.otsu_segmentation(k=3) #0=bg,1=csf,2=gm,3=wm

    """

    if mask is not None:

        image = image.mask_image(mask)

    seg = image.threshold_image('Otsu', k)

    return seg