OpenCV: Grayscale image displayed in greenish color [duplicate]

问题

This question already has answers here:

Show grayscale OpenCV image with matplotlib (1 answer)

plt.imshow shows color images for grayscale images in IPython (1 answer)

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I am doing my first steps using OpenCV (version 3.3.0 from opencv-python package on Mac OS). Using OpenCV inside jupyter notebook and displaying a greyscale image through matplotlibresults in a greenish image instead of a greyscale one.

%matplotlib inline

import cv2 as cv
import numpy as np

import matplotlib.pyplot as plt

plt.rcParams['figure.figsize'] = (8.0, 8.0)

img = cv.imread('IMG_20171212_222022.jpg', cv.IMREAD_GRAYSCALE)

plt.imshow(img)

Do you know where this comes from? Is this a bug or desired behavior?

来源：https://stackoverflow.com/questions/47782311/opencv-grayscale-image-displayed-in-greenish-color