Jupyter 中 plt.imshow() 和 cv2.imshow() 的不同结果

Question

I'm trying to change to image color to Gray on Jupyter Notebook it's confusing that using the cv2.imshow("gray", gray_image) can show the grayscale image in the alert window. Result of cv2.imshow("gray", gray_image)

And I use the plt.imshow(gray_image) can not show the grayscale image but it is green. Result of plt.imshow(gray_image)

So, how can I show the grayscale which is the result of cv2.imshow(gray_image) on Jupyter Notebook? Thank You Here are my code:

import cv2
from  matplotlib import pyplot as plt
%matplotlib inline

filename = 'photo.jpg'
img = cv2.imread('cat.jpg')
img = cv2.resize(img, (540, 540))
gray_image = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
#using cv2
cv2.imshow("gray",gray_image)
cv2.waitKey(0)
#using plt
plt.imshow(gray_image)

Answer 1

If you do not want to use CV, just use cmap and map it to the grayscale. imshow works pretty well here.

import numpy as np
import matplotlib.pyplot as plt
from PIL import Image

fname = 'Capture.png'
image = Image.open(fname).convert("L")
arr = np.asarray(image)
plt.imshow(arr, cmap='gray', vmin=0, vmax=255)
plt.show()