functions.py 文件源码

def bilinear_interpolation_kernel(in_channels, out_channels, ksize):
    """calculate a bilinear interpolation kernel

    Args:
        in_channels (int): Number of channels of input arrays. If ``None``,
            parameter initialization will be deferred until the first forward
            data pass at which time the size will be determined.
        out_channels (int): Number of channels of output arrays.
        ksize (int): Size of filters (a.k.a. kernels).
    """

    factor = (ksize + 1) / 2
    if ksize % 2 == 1:
        center = factor - 1
    else:
        center = factor - 0.5
    og = np.ogrid[:ksize, :ksize]
    k = (1 - abs(og[0] - center) / factor) * (1 - abs(og[1] - center) / factor)

    W = np.zeros((in_channels, out_channels, ksize, ksize)).astype(np.float32)
    W[range(in_channels), range(out_channels), :, :] = k
    return W