from PIL import Image

def BW(infile):
    #infile = 'proj3.jpg'
    myImage = Image.open(infile)
    myImage.show()

    #Convert your opened image into RGB format
    myImage = myImage.convert('RGB')
    width, height = myImage.size

    #Process the image into black and write
    for x in range(width):
        for y in range(height):
            r,g,b = myImage.getpixel((x,y))
            greylevel = int(round(r/3+g/3+b/3))
            myImage.putpixel((x,y), (greylevel, greylevel, greylevel))

    # Save the modified image and display
    outfile = infile[:-4]
    outfile = outfile + "_bw.jpg"
    myImage.save(outfile)
    myImage.show()

BW("proj3.jpg")