This method cleans input image by replacing all pixels with RGB values
from -4473925 (gray) to -1 (white) with white pixels and
from -4473925 (gray) to -16777216 (black) with black pixels
This method cleans input image by replacing all pixels with RGB values
from -3092272 (light gray) to -1 (white) with white pixels and
from -3092272 (light gray) to -16777216 (black) with black pixels