identify not white pixels in bmp

[deanhystad]

I think that should work, but it can be simplified. Compute the ratio of pixels that are the most common color. Compare ratio to a threshold.

from PIL import Image
import numpy as np

def primary_color_ratio(image):
    """Return ratio of pixels that are the "background" color."""
    pixels = np.array(image.getdata())
    _, counts  = np.unique(pixels, axis=0, return_counts=True)
    return max(counts) / (max(len(pixels), 1)


print(primary_color_ratio(Image.new("RGB", (10, 10), (255, 0, 0))))
print(primary_color_ratio(Image.open("test.jpg")))

Output:
1.0
0.032