Resize an ND array with interpolation.

    Scaling factors for spatial dimensions are determined by either
    ``scale`` or ``output_size``.

    ``nd = len(scale)`` or ``nd = len(output_size)`` determines the number of
    spatial dimensions, and the last ``nd`` dimensions of the input ``x`` are    
    considered as the spatial dimensions to be resized.


    If ``scale`` is given, the ``output_size`` is calculated by
    ``output_size[i] = floor(scale[i] * x.shape[i - len(scale)])``.

    Example:

    .. code-block:: python

        import numpy as np
        import nnabla as nn
        import nnabla.functions as F

        x_data = np.random.rand(64, 3, 224, 224)
        x = nn.Variable.from_numpy_array(x_data)

        # Resize by scales
        y = F.interpolate(x, scale=(2, 2), mode='linear')
        print(y.shape)  # (64, 3, 448, 448)
        y.forward()
        print(y.d)  # Print output

        # Resize to a size
        y2 = F.interpolate(x, output_size=(320, 257), mode='linear')
        print(y2.shape)  # (64, 3, 320, 257)
        y2.forward()
        print(y2.d)  # Print output

    Args:
        x(~nnabla.Variable): N-D array with an arbitrary number of dimensions.
        scale(tuple of ints): Scale factors along axes. The default is
            ``None``, and if this is omitted, ``output_size`` must be specified.
        output_size(tuple of ints): The output sizes for axes. If this is
            given, the scale factors are determined by the output sizes and the
            input sizes. The default is ``None``, and if this is omitted,
            ``scale`` must be specified.
        mode(str): Interpolation mode chosen from ('linear'|'nearest').
            The default is 'linear'.
        align_corners(bool): If true, the corner pixels of input and output
            arrays are aligned, such that the output corner pixels have the
            same values with the input corner pixels.
            The default is ``None``, and it becomes ``True`` if mode is
            'linear', otherwise ``False``.

    Returns:
        ~nnabla.Variable: N-D array.

def interpolate(x, scale=None, output_size=None, mode='linear', align_corners=None):
    '''
    Resize an ND array with interpolation.

    Scaling factors for spatial dimensions are determined by either
    ``scale`` or ``output_size``.

    ``nd = len(scale)`` or ``nd = len(output_size)`` determines the number of
    spatial dimensions, and the last ``nd`` dimensions of the input ``x`` are    
    considered as the spatial dimensions to be resized.


    If ``scale`` is given, the ``output_size`` is calculated by
    ``output_size[i] = floor(scale[i] * x.shape[i - len(scale)])``.

    Example:

    .. code-block:: python

        import numpy as np
        import nnabla as nn
        import nnabla.functions as F

        x_data = np.random.rand(64, 3, 224, 224)
        x = nn.Variable.from_numpy_array(x_data)

        # Resize by scales
        y = F.interpolate(x, scale=(2, 2), mode='linear')
        print(y.shape)  # (64, 3, 448, 448)
        y.forward()
        print(y.d)  # Print output

        # Resize to a size
        y2 = F.interpolate(x, output_size=(320, 257), mode='linear')
        print(y2.shape)  # (64, 3, 320, 257)
        y2.forward()
        print(y2.d)  # Print output

    Args:
        x(~nnabla.Variable): N-D array with an arbitrary number of dimensions.
        scale(tuple of ints): Scale factors along axes. The default is
            ``None``, and if this is omitted, ``output_size`` must be specified.
        output_size(tuple of ints): The output sizes for axes. If this is
            given, the scale factors are determined by the output sizes and the
            input sizes. The default is ``None``, and if this is omitted,
            ``scale`` must be specified.
        mode(str): Interpolation mode chosen from ('linear'|'nearest').
            The default is 'linear'.
        align_corners(bool): If true, the corner pixels of input and output
            arrays are aligned, such that the output corner pixels have the
            same values with the input corner pixels.
            The default is ``None``, and it becomes ``True`` if mode is
            'linear', otherwise ``False``.

    Returns:
        ~nnabla.Variable: N-D array.

    '''
    from .function_bases import interpolate as interpolate_base
    import math
    if scale is None and output_size is None:
        raise ValueError('Either scale or output_size must be given')
    elif output_size is None:
        output_size = [int(math.floor(s * d))
                       for d, s in zip(x.shape[-len(scale):], scale)]
    if align_corners is None:
        if mode == 'linear':
            align_corners = True
        else:
            align_corners = False
    return interpolate_base(x, output_size, mode, align_corners)