Convert RGB to black OR white

Question

How would I take an RGB image in Python and convert it to black OR white? Not grayscale, I want each pixel to be either fully black (0, 0, 0) or fully white (255, 255, 255).

Answer 1

I would suggest converting to grayscale, then simply applying a threshold (halfway, or mean or meadian, if you so choose) to it.

from PIL import Image

col = Image.open('myimage.jpg')
gry = col.convert('L')
grarray = np.asarray(gry)
bw = (grarray > grarray.mean())*255
imshow(bw)

Answer 2

Pillow, with dithering

Using pillow you can convert it directly to black and white. It will look like it has shades of grey but your brain is tricking you! (Black and white near each other look like grey)

from PIL import Image 
image_file = Image.open("cat-tied-icon.png") # open colour image
image_file = image_file.convert('1') # convert image to black and white
image_file.save('/tmp/result.png')

Original:

Converted: