Tensorflow 读取图片，像素强度，归一化，区间转换为[-1,1]

# -*- coding:utf-8 -*-

import tensorflow as tf
import numpy as np
import cv2

#narry
img_r = cv2.imread('img_r.png')

# img_r=img_r*1.0/255*2-1
img_r=np.float32(img_r)
img_r=(img_r-128)/128


print (img_r)