Python save and read a grayscale image in two dimension array?

Question

I want to save an image without any channel, so the dimension would only be 2. Thus, is there a way I do it in matplotlib?

I have already tried using

matplotlib.pyplot.imsave('img.png', image, cmap='gray')

but when I read it using

matplotlib.pyplot.imread('img.png')

The dimension is 3. So I'm confusing how. I know maybe I can't use imread but what can I do instead?

A grayscale image has 3 dimention, the third one represent light level — Ando
– Ando, Commented Sep 5, 2020 at 9:37
Thank you! Already changed the question. So do you know how to make them 2 dimension? like array.shape = (256,256), not (256,256,3) ? — Walker
– Walker, Commented Sep 5, 2020 at 9:39
You meant (256,256, 1) right ? because (256,256) is not an image — Ando
– Ando, Commented Sep 5, 2020 at 9:42
@YukiShioriii: That makes no sense. A gray-scale image is a 2D matrix. — Cris Luengo
– Cris Luengo, Commented Sep 5, 2020 at 14:28
From the docs, it looks like matplotlib only saves RGB or RGBA format image files. You’ll have to use a different package to save a gray-scale image. OpenCV as suggested below is just one option. There are many. Try PIL. — Cris Luengo
– Cris Luengo, Commented Sep 5, 2020 at 14:32

Dwa · Accepted Answer · 2020-09-05 17:41:22Z

1

If you have opencv installed, you can try:

cv2.imread('1.png', cv2.IMREAD_GRAYSCALE)

Also, you can also try PIL.

from PIL import Image
Image.fromarray(array)

I didn't see this one on the internet, but this one works! thanks to my teacher!

skimage.io.imsave('1.png', np.around(image*255).astype(np.uint8))

To use this, you have to have skimage preinstalled.

pip3 install scikit-image

Thanks @Cris Luengo in the comment above to point out that

"From the docs, it looks like matplotlib only saves RGB or RGBA format image files. You’ll have to use a different package to save a gray-scale image. OpenCV as suggested below is just one option. There are many. Try PIL."

Give him an upvote when you saw it!

edited Sep 5, 2020 at 17:41

answered Sep 5, 2020 at 10:21

Dwa

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