clean_greyscale.py

'''
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This script takes in a folder of images and makes them all greyscale images.
Doing this often increases machine learning accuracy by only focusing on 
relevant features and not color distortions in images.

This is enabled if default_image_cleaners=['clean_greyscale']
'''
import numpy as np
from PIL import Image
import os, cv2

def rgb2gray(rgb):
        return np.dot(rgb[...,:3], [0.2989, 0.5870, 0.1140])

def clean_greyscale(imagefile):
    img = cv2.imread(imagefile)
    os.remove(imagefile)
    gray = rgb2gray(img)    
    cv2.imwrite(imagefile, gray)
    return [imagefile]