Python - Is Base64 Data A Valid Image?

I am using Python and I have a base64 string. I want to know that if the base64 data I have received is a image and not any other file (eg. PDF, DOCX) whose extension is changed to

Solution 1:

The PNG format has a fixed header that consists of the 8 bytes 89 50 4e 47 0d 0a 1a 0a which, when converted to base64, look like this:

iVBORw0KGgo=

As you can see, it ends with a padding character "=", which will not be there in a real base64 representation of an image, and instead of "o" there could be a different character depending on the bytes after the header.

So you can easily recognize a base64 encoded PNG by comparing the first characters of the base64 string with

iVBORw0KGg

This principle works for all file formats that have a fixed header.

Solution 2:

With the help of this function, I check 3 things:

1. checking base64 image string validation
2. checking format of image that I want to support
3. checking image dimentions

Code:

import base64
import io
from PIL import Image


defis_valid_base64_image(self, image_string):
    # checking valid base64 image string try:
        image = base64.b64decode(image_string)
        img = Image.open(io.BytesIO(image))
    except Exception:
        raise Exception('file is not valid base64 image')
    # end of check base64 image string# checking image format I want to supportif img.format.lower() in ["jpg", "jpeg", "png"]:
        
        # if you need to check image dimension
        width, height = img.size
        if width < 800and height < 800:
            returnTrueelse:
            raise Exception(
                'image size exceeded, width and height must be less than 800 pixels')
        # end of checking dimentionselse:
        raise Exception('Image is not valid, only \'base64\' image (jpg, jpeg, png) is valid')
    # end of checking image format