bw_detector.py

from PIL import Image, ImageStat
import os

def detect_color_image(file, thumb_size=40, MSE_cutoff=22, adjust_color_bias=True):
    pil_img = Image.open(file)
    bands = pil_img.getbands()
    if bands == ('R','G','B') or bands== ('R','G','B','A'):
        thumb = pil_img.resize((thumb_size,thumb_size))
        SSE, bias = 0, [0,0,0]
        if adjust_color_bias:
            bias = ImageStat.Stat(thumb).mean[:3]
            bias = [b - sum(bias)/3 for b in bias ]
        for pixel in thumb.getdata():
            mu = sum(pixel)/3
            SSE += sum((pixel[i] - mu - bias[i])*(pixel[i] - mu - bias[i]) for i in [0,1,2])
        MSE = float(SSE)/(thumb_size*thumb_size)
        if MSE <= MSE_cutoff:
            #print ("grayscale\t")
            return(0)
        else:
            #print ("Color\t\t\t")
            return(1)
        #print ("MSE = ",MSE)
    elif len(bands)==1:
        #print ("Black and white", bands)
        return(0)
    else:
        #print ("Don't know...", bands)
        return(1)