Save numpy array as single channel png with custom colors

Question

I have an integer numpy array representing image with few values (about 2-5). And I would like to save it to png file with custom color for every value. I was trying it like thi

Answer 1

You can make a palette image like this:

#!/usr/bin/env python3

from PIL import Image
import numpy as np

# Make image with small random numbers
im = np.random.randint(0,5, (4,8), dtype=np.uint8)

# Make a palette
palette = [255,0,0,    # 0=red
           0,255,0,    # 1=green
           0,0,255,    # 2=blue
           255,255,0,  # 3=yellow
           0,255,255]  # 4=cyan
# Pad with zeroes to 768 values, i.e. 256 RGB colours
palette = palette + [0]*(768-len(palette))

# Convert Numpy array to palette image
pi = Image.fromarray(im,'P')

# Put the palette in
pi.putpalette(palette)

# Display and save
pi.show()
pi.save('result.png')