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, #FFFFFF, #000000]]

I feel like I may need to download PIL, but I cannot tell what the module does from their website. I also need to be able to generate images from these types of arrays. Thank you!

Martin Geisler · Accepted Answer · 2012-02-04 19:01:45Z

3

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.

edited Feb 4, 2012 at 19:01

answered Feb 4, 2012 at 18:55

Martin Geisler

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3 Comments

user1189737 Over a year ago

Thanks, exactly what I was looking for. Only one question: how do I move to three color channels? I assume each pixel is a 3-tuple but what do put instead of "L"?

Martin Geisler Over a year ago

It's right there in the manual: you use RGB as the mode for three channels.

Martin Geisler Over a year ago

@user1189737: oh, sorry! I didn't see you were so new here :-) Thanks!

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