Convert boolean numpy array to pillow image
Update
This bug has now been solved in Pillow==6.2.0. The link to the issue on GitHub is here.
If you cannot update to the new version of Pillow, please see below.
PIL's Image.fromarray
function has a bug with mode '1' images. This Gist demonstrates the bug, and shows a few workarounds. Here are the best two workarounds:
import numpy as np
from PIL import Image
# The standard work-around: first convert to greyscale
def img_grey(data):
return Image.fromarray(data * 255, mode='L').convert('1')
# Use .frombytes instead of .fromarray.
# This is >2x faster than img_grey
def img_frombytes(data):
size = data.shape[::-1]
databytes = np.packbits(data, axis=1)
return Image.frombytes(mode='1', size=size, data=databytes)
Also see Error Converting PIL B&W images to Numpy Arrays.