How do I normalize an image?

Question

If I have a series of pixels, which range from say -500 to +1000, how would I normalize all the pixels on the same gradient so that they fall between a specific range, say 0

Answer 1

Some pseudo code may help:

foreach( pixel_value in pixel_values): # between -500 and 1000

    position = (pixel_value + 500) / 1500 # gives you a 0 to 1 decimal
    new_value = int(postion * 255) # or instead of casting, you could round it off

That's python code by the way.