__all__ = ['integrate_velocity_field']

import ants

from ants.internal import get_lib_fn

def integrate_velocity_field(velocity_field,

                             lower_integration_bound=0.0,

                             upper_integration_bound=1.0,

                             number_of_integration_steps=10):

    """

    Integrate velocity field.

    Arguments

    ---------

    velocity_field : ANTsImage velocity field

        time-varying displacement field

    lower_integration_bound: float

        Lower time bound for integration in [0, 1]

    upper_integration_bound: float

        Upper time bound for integration in [0, 1]

    number_of_integation_steps: integer

        Number of integration steps used in the Runge-Kutta solution

    Example

    -------

    >>> import ants

    >>> fi = ants.image_read( ants.get_data( "r16" ) )

    >>> mi = ants.image_read( ants.get_data( "r27" ) )

    >>> reg = ants.registration(fi, mi, "TV[2]")

    >>> velocity_field = ants.image_read(reg['velocityfield'][0])

    >>> field = ants.integrate_velocity_field(velocity_field, 0.0, 1.0, 10) 

    >>> temp=ants.apply_ants_transform_to_image( 

        ants.transform_from_displacement_field( field ), mi, fi )

    """

    libfn = get_lib_fn('integrateVelocityFieldD%i' % (velocity_field.dimension-1))

    integrated_field = libfn(velocity_field.pointer, lower_integration_bound,

        upper_integration_bound, number_of_integration_steps)

    new_image = ants.from_pointer(integrated_field).clone('float')

    return new_image