我如何使用tensorflow变换来处理图像，例如，定义一个操作来减少图像的平均值

import tensorflow as tf
import numpy as np
import matplotlib.pyplot as plt

image = plt.imread('image.jpg')  # 加载图像
image = image.astype(np.float32)  # 转换数据类型为float32
image = np.expand_dims(image, axis=0)  # 添加批次维度

input_image = tf.placeholder(tf.float32, shape=(None, None, None, 3))  # 定义输入图像的占位符
mean_value = tf.reduce_mean(input_image, axis=(1, 2))  # 计算图像的平均值
subtract_mean = tf.subtract(input_image, tf.expand_dims(mean_value, axis=(1, 2)))  # 减去平均值

with tf.Session() as sess:
    subtracted_image = sess.run(subtract_mean, feed_dict={input_image: image})  # 运行操作