Incorrect output

[missionfloyd]

I've noticed that images produced with hitherdither are slightly different than those produced with other programs using the same algorithms.

I tested this using Floyd-Steinberg on a solid 50% gray image, which should produce a uniform checkerboard pattern.

Input	Output	Expected (from PIL)

I've found that by rounding when distributing the quantization error, the above image renders correctly, while others are closer but still different.
ni[yn, xn] += np.round(quantization_error * diffusion_coefficient)
Maybe that's as good as it's gonna get.

[Henrik Blidh]

Interesting. How did you create the PIL image? If PIL works better, then I would suggest using that.

[missionfloyd]

from PIL import Image

img = Image.open('808080.png') # solid grey image
img_dithered = img.convert('1') # uses floyd-steinberg dithering by default
img_dithered.save('dithered.png')

PIL only supports Floyd-Steinberg, however.