The computer doesn't care though.
An inverted image does look more impressive than just the regular one I guess.
I just mean to say it's easier to discover a method to crack the captcha if you fiddle with the image in photoshop first. If you notice that inverting/grayscaling the image results in something easily detected you can just mimic that with code.
def neoOCR(self, im):
im = im.convert("L")
lo, hi = im.getextrema()
lo = im.point(lambda x: x == lo)
x, y, _, _ = lo.getbbox()
return x + 3, y + 2
