Quick NumPy usage example

test.py

#!/usr/bin/python
# coding=utf-8

# Import everything you need for image processing
from pylab import *

# This is an addon that's needed to be able to save the image
from scipy.misc import imsave

# Read image called "input.jpg" (rename that to whatever you want)
image = imread ("input.jpg")

# Create a vertical red line :
#   * Starts at the 40th column
#   * Height is the image's height
#   * Width is 20px (so 40th col -> 60th col)
image[:, 40:60, 0] = 255 # RED
image[:, 40:60, 1] = 0   # GREEN
image[:, 40:60, 2] = 0   # BLUE

# You can also replicate part of an image using the same syntax
image[:, 150:170, :] = image[:, 170:190, :]

# Show image (useful for quick tests)
imshow (image)
show()

# Save image to test.jpg
imsave ("test.jpg", image)