random_noise about ctf HOT 2 CLOSED

from PIL import Image

img = Image.open('second.png')
data = list(img.getdata())

width, height = img.size
out_image = ''

hist = {}
for p in data:
    hist[p] = hist.get(p, 0) + 1

for p in data:
    if hist[p] < 10:
        out_image += '\xff'
    else:
        out_image += '\x00'

with open('out.data', 'wb') as f:
    f.write(out_image)