Simple python color flatting

#!/usr/bin/python

import Image, ImageDraw, ImageColor, random, sys, timeit

starttime=timeit.default_timer()

im = Image.open(str(sys.argv[1])).convert('RGB')

def flood(posx,posy,color):
    ImageDraw.floodfill(im, (posx,posy), color, border=None)

def RandomColor():
    hue=random.randint(0,360)
    return ImageColor.getrgb("hsl("+str(hue)+",100%,50%)")


def getAllPixels(replace):
    dimensions=im.size

    for posy in range(dimensions[1]):
        for posx in range(dimensions[0]):
            CheckPixel(posx,posy,replace)

def CheckPixel(posx,posy,replace):
    pixelColor=(im.load()[posx,posy])
    if pixelColor==replace:
        if replace==(255,255,255):
            flood(posx,posy,RandomColor())
        else:
            flood(posx,posy,(255,255,255))
    else:
        pass

def elapsed():
    return str(int(timeit.default_timer()-starttime))


getAllPixels((255,255,255))
print("Pass 1 completed in "+elapsed()+" seconds")
getAllPixels((0,0,0))

im.save("output.png", "PNG")
print("Script completed in "+elapsed()+" seconds")