CODEWITHSUNDEEP
pythonnumpypython-imaging-librarypngcolor-palette
Dre
Dre

Reputation: 723

How to retain the colors of a PNG image when converting back from an array

Whenever I convert a PNG image to a np.array and then convert it back to a PNG I lose all the colors of the image. I would like to be able to retain the colors of the original PNG when I am converting it back from a np.array.

Original PNG Image

enter image description here

My code:

from PIL import Image    

im = Image.open('2007_000129.png')
im = np.array(im)

#augmenting image
im[0,0] = 1

im = Image.fromarray(im, mode = 'P')

Outputs a black and white version of the image

enter image description here

I also try using getpalette and putpalette but this does not work it just returns a NonType object.

im = Image.open('2007_000129.png')
pat = im.getpalette()
im = np.array(im)
im[0,0] = 1
im = Image.fromarray(im, mode = 'P')
im= im.putpalette(pat)

Upvotes: 0

Views: 1079

Answers (2)

HansHirse
HansHirse

Reputation: 18895

Using the second code provided, the error comes from this line:

im= im.putpalette(pat)

If you refer to the documentation of Image.putpalette, you see that this function doesn't return any value, thus Image.putpalette is applied to the corresponding image directly. So, (re-)assigning the non-existent return value (which then is None) is not necessary – or, as seen here, erroneous.

So, the simple fix is just to use:

im.putpalette(pat)

Using this change, the second code provided works as intended.

Upvotes: 1

Alex Rancea
Alex Rancea

Reputation: 87

Your image is using single channel color using palette. Try the code below. Also you can check more about this subject at What is the difference between images in 'P' and 'L' mode in PIL?

from PIL import Image    
import numpy as np


im = Image.open('gsmur.png')
rgb = im.convert('RGB')
np_rgb = np.array(rgb)
p = im.convert('P')
np_p = np.array(p)

im = Image.fromarray(np_p, mode = 'P')
im.show()
im2 = Image.fromarray(np_rgb)
im2.show()

Upvotes: 3

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