我正在研究医学图像正是 CT 扫描图像，有一种读取此类图像的方法，还有另一种重采样方法，两种方法的代码如下所示：

def load_itk_image(filename):
    # read infos from route
    itkimage = sitk.ReadImage(filename)
    # read imagearray
    numpyImage = sitk.GetArrayFromImage(itkimage)
    # read coords
    # the given coords and spacing comes: x, y, z and we should transfer it to z, y, x
    numpyOrigin = np.array(list(reversed(itkimage.GetOrigin())))
    numpySpacing = np.array(list(reversed(itkimage.GetSpacing())))

    return numpyImage, numpyOrigin, numpySpacing

def resample(image,oldspacing,newspacing):
    start_time = time.time()
    resize_factor = np.array(oldspacing).astype(np.float)/np.array(newspacing).astype(np.float)
    new_real_shape = image.shape * resize_factor
    new_shape = np.round(new_real_shape)
    real_resize_factor = new_shape/image.shape
    image = scipy.ndimage.interpolation.zoom(image, real_resize_factor, mode = "nearest")
    print("%s time takes in seconds" % (time.time() - start_time))
    return np.array(image)

我的问题是，重新采样功能需要大量时间来重新采样一张 2d 图像大约需要 30 秒，为什么要花这么多时间？有什么方法可以减少重采样时间？