如何修改灰度图像？

Question

我正在从事隐写术项目。不使用PIL 我已经将封面图片复制到另一个变量中 将封面图像分成块 在方块上做了一些操作 现在，我想从块中的对应像素替换封面图像的每个像素 最后，显示图片

img = imread('Lena.jpg') # cover image 
row ,col = img.shape
imgx = img[:] 
blocksize = 3 

block=[]
block = divideintoblocks()# size of each  block 3*3  
#total 171*171 blocks of 3*3 for a 513*513 image
bcnt = 0 # number of block count
for block in blocks:
  for i in range(r):
      for j in range(c):
         px = bcnt / numberOfBlocks # finding row of corresponding block 
         py = bcnt % numberOfBlocks # finding col of correspondong block 
         imgx[px * blocksize +i ][ py * blocksize + j] = block[i][j]

      bcnt+=1