Python: how do you create an array with information about each pixel from an image?

Question

For example, a 3 pixel by 3 pixel jpeg image of a checkerboard should be something like

[[#000000, #FFFFFF, #000000],
[#FFFFFF, #000000, #FFFFFF],
[#000000, #FFF         


        

Answer 1

Use the Image.getdata method. The method returns a generator that you can iterate over:

from PIL import Image
img = Image.open("a.png")
data = img.getdata()
for (r, g, b, a) in data:
    # do something with the pixel values

To go the other way you use Image.putdata. This generates a tiny checkerboard picture:

>>> img = Image.new("L", (3, 3))
>>> data = [0, 255, 0, 255, 0, 255, 0, 255, 0]
>>> img.putdata(data)
>>> img.save("checkerboard.png")

Here I created a grayscale image (only one "luminescence" channel) and so I just used a single integer value for each pixel.