CODEWITHSUNDEEP
pythonnumpyopencvmatplotlib
RC0993
RC0993

Reputation: 958

How to get numpy.zeros() and (numpy.ones() * 255) to produce a black and white image respectively?

I am new to Python + OpenCV, so this might be a basic question for most of you, as I couldn't find a good/ satisfactory solution for this online.

So I am trying to create an Image by separately creating R-G-B layers
R - Layer of 0s
G - Layer of 255s
B - Layer of 255*Identity matrix

import cv2 as cv
import numpy as np
import matplotlib.pyplot as plt

Red = np.zeros([6, 6], dtype = np.uint8)
plt.imshow(Red)        # it is just the red layer which is actually all black
plt.show()

Green = np.ones([6, 6], dtype = np.uint8) * 255
plt.imshow(Green)      # it is just the Green layer which is actually all white
plt.show()

Blue = np.eye(6, dtype = int) * 255
plt.imshow(Blue)       # it is just the Blue layer which is actually black with white diag
plt.show()

But I am actually getting a Purple or combination of purplr and yellow. My Output

Can someone explain what's happening and/or how to solve it?

Upvotes: 1

Views: 2086

Answers (1)

Amit Gupta
Amit Gupta

Reputation: 2918

Try using

Blue = np.eye(6, dtype = int) * 255
plt.imshow(Blue, cmap='gray', vmin=0, vmax=255)
plt.show()

for more reference this answer

Upvotes: 5

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