Image processing with numpy arrays

Question

In the grayscale mode, 255 indicates white. So if all elements of the numpy matrix are 255, should not it be a white image?

l = np.full((184,184),255)
j = Image.fromarray(l,'L')
j.show()

I am getting a black-and-white vertical striped image as output instead of pure white image. Why is it so?

confirm.. I got the same result using Canopy/ipython on Windows10. What's odd is when I change array size to 185,185, the lines all go diagonal. 184,184 = vertical lines. — zipzit
– zipzit, Commented Apr 11, 2018 at 16:54
yes, my project was not working due to this and finally after lots of debugging, I found this as the issue — Surabhi Amit Chembra
– Surabhi Amit Chembra, Commented Apr 11, 2018 at 16:57

zipzit · Accepted Answer · 2018-04-11 17:09:47Z

1

The issue is the 'L' Mode. L = 8 bit pixels, black and white. The array you created is likely 32 bit values.

Try j = Image.fromarray(l, 'I') ## (32-bit signed integer pixels)

(note: Many thanks to you for introducing me to the Pillow Image module for Python with this posting...)

Complete test code:

from PIL import Image
import numpy as np
l = np.full((184,184),255)
j = Image.fromarray(m, 'I')
j.show()

answered Apr 11, 2018 at 17:04

zipzit

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1 Comment

Thanks, I used image.convert('L') to change it into required grayscale mode, ie, j.convert('L')