deform_conv.py 文件源码

def th_map_coordinates(input, coords, order=1):
    """Tensorflow verion of scipy.ndimage.map_coordinates
    Note that coords is transposed and only 2D is supported
    Parameters
    ----------
    input : tf.Tensor. shape = (s, s)
    coords : tf.Tensor. shape = (n_points, 2)
    """

    assert order == 1
    input_size = input.size(0)

    coords = torch.clamp(coords, 0, input_size - 1)
    coords_lt = coords.floor().long()
    coords_rb = coords.ceil().long()
    coords_lb = torch.stack([coords_lt[:, 0], coords_rb[:, 1]], 1)
    coords_rt = torch.stack([coords_rb[:, 0], coords_lt[:, 1]], 1)

    vals_lt = th_gather_2d(input,  coords_lt.detach())
    vals_rb = th_gather_2d(input,  coords_rb.detach())
    vals_lb = th_gather_2d(input,  coords_lb.detach())
    vals_rt = th_gather_2d(input,  coords_rt.detach())

    coords_offset_lt = coords - coords_lt.type(coords.data.type())

    vals_t = vals_lt + (vals_rt - vals_lt) * coords_offset_lt[:, 0]
    vals_b = vals_lb + (vals_rb - vals_lb) * coords_offset_lt[:, 0]
    mapped_vals = vals_t + (vals_b - vals_t) * coords_offset_lt[:, 1]
    return mapped_vals