dithering.py

#Based off coding train:
#https://github.com/CodingTrain/Rainbow-Code/blob/master/CodingChallenges/CC_90_dithering
from PIL import Image,ImageDraw
img = Image.open("kitten.jpg").convert("L").convert("RGB")
d = ImageDraw.Draw(img)
for y in range(img.height-1):
    for x in range(1,img.width-1):
        oldC = img.getpixel((x,y))
        factor = 1
        newC = []
        for i in oldC:
            newC.append(int(round(factor*i/255)*(255/factor)))
        newC = tuple(newC)
        d.point((x,y),fill=newC)
        errC = []
        for i in range(3):
            errC.append(oldC[i]-newC[i])
        errC = tuple(errC)
        indexes = [(x+1,y),(x-1,y+1),(x,y+1),(x+1,y+1)]
        numbers = (7,5,3,1)
        for i in range(3):
            try:
                c = img.getpixel(indexes[i])
            except IndexError:
                print(indexes[i])
            color = []
            for sex in range(3):
                color.append(int(c[sex] + errC[sex] * numbers[i]/16))
            color = tuple(color)
            d.point(indexes[i],fill=color)

img.show()