How to change pixel color in Python

Question

How do you change just the color of some pixels from an image that are not in a predefined list ? I tried something like this:

from PIL import Image
picture = Image.open("// location")

imshow (picture)

_colors = [[0, 128, 0], [128, 128, 0], [128, 128, 128], [192, 128, 0], [128, 64, 0],    [0, 192, 0], [128, 64, 128], [0, 0, 0]]
 width, height = picture.size

for x in range(0, width-1):
 for y in range(0, height-1):
  current_color = picture.getpixel( (x,y) )
  if current_color!= _colors[0] and current_color!= _colors[1] and current_color!= _colors[2] and current_color!= _colors[3] and current_color!= _colors[4] and  current_color!= _colors[5] and current_color!= _colors[6] and current_color!= _colors[7]:
   picture.putpixel( (x,y), (0, 0, 0))

  imshow (picture)

I want to make just some pixels black, but somehow this would return a black image altogether

Answer 1

This line :

if current_color!= _colors[0] and current_color!= _colors[1] and current_color!= _colors[2] and current_color!= _colors[3] and current_color!= _colors[4] and  current_color!= _colors[5] and current_color!= _colors[6] and current_color!= _colors[7]:

always returns True, so you iterate over the whole picture, changing it to black. getpixel returns a tuple :

>>> print picture.getpixel((1, 1))
   (79, 208, 248)

and you compare it to a list( [0,128,0]). They are not the same:

>>> (1,2,3) == [1,2,3]
False

change colors to a list of tuples rather than a list of lists.

Answer 2

keep the type of pixel data the same and shorten that if statement with an "in"

import Image
filename ="name.jpg"

picture = Image.open(filename, 'r')
_colors = [(0, 128, 0), (128, 128, 0), (128, 128, 128), (192, 128, 0), (128, 64, 0), (0, 192, 0), (128, 64, 128), (0, 0, 0)]
width, height = picture.size

for x in range(0, width):
    for y in range(0, height):
        current_color = picture.getpixel((x,y))
        if current_color in _colors:
            picture.putpixel((x,y), (0, 0, 0))

picture.show()