Home/ Questions/Q 9118241
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-17T05:05:57+00:00

Using Python ‘s PIL module, we can read an digital image into an array

  • 0

Using Python‘s PIL module, we can read an digital image into an array of integers,

from PIL import Image
from numpy import array

img = Image.open('x.jpg')
im = array(img)  # im is the array representation of x.jpg

I wonder how does PIL interpret an image as an array? First I tried this 

od -tu1 x.jpg

and it indeed gave a sequence of numbers, but how does PIL interpret a color image into a 3D array?

In short, my question is that I want to know how can I get a color image’s array representation without using any module like PIL, how could do the job using Python?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Well, it depends on the image format I would say.

    For a .jpg, there is a complete description of the format that permits to read the image .
    You can read it here

    What PIL does is exactly what you did at first. But then it reads the bytes following the specifications, which allow it to transform this into a human readable format (in this case an array).

    It may seem complex for JPEG, but if you take png (the version without compression) everything can seem way more simple.
    For example this image

    png image without compression

    If you open it, you will see something like that :
    Raw dump of previous png image

    You can see several information on top that corresponds to the header.

    Then you see all those zeroes, that are the numerical representation of black pixels of the image (the top left corner).

    If you open the image with PIL, you will get an array that is mostly filled with 0.

    If you want to know more about the first bytes, look at the png specifications chapter 11.2.2.

    You will see that some of the bytes corresponds to the width and height of the image. This is how PIL is able to create the array :).

    Hope this helps !

    • 0