Converting data:image from base64 to JPEG in Python

Question

From the client's POST submission, we are successfully receiving an image in the following format, data:image/jpeg;base64,/9j/.... and an image file is being generated by the following code:

@app.route('/submission', methods=('GET', 'POST'))
def submission():
    
    if request.method == 'POST':
        
        raw_image = request.form['file']
        #Problem Starts Here
        # this doesn't work either: 
        # raw_image = raw_image.replace("data:image/jpeg;base64,/9j/", '');
        with open(UPLOADED_IMAGES_DEST+'/image.jpeg', 'wb') as fh:
            fh.write(base64.decodebytes(raw_image))
        #Problem Ends Here
        return jsonify(request.form)
        
    return render_template('submission.html')

However, the image cannot be opened as it's an "Invalid or Unsupported Format". I'm trying to improve the conversion process so it will produce a viewable JPEG image.

Beginning of `raw_image`:

data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgMCAgMDAwMEAwMEBQgFBQQEBQoHBwYIDAoMDAsKCwsNDhIQDQ4RDgsLEBYQERMUFRUVDA8XGBYUGBIUFRT/2wBDAQMEBAUEBQkFBQkUDQsNFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBT/wAARCADwAUADASIAAhEBAxEB/8QAHQAAAgIDAQEBAAAAAAAAAAAABQYEBwIDCAEACf/EAEwQAAEDAwMCBAQEAwUFBQQLAAECAxEABAUGEiExQQcTUWEIInGBFDKRoRVCUiOxwdHwJGJyouEJFjOSwhdDgvEmU2ODk7LDxNLU4v/EABsBAAMBAQEBAQAAAAAAAAAAA...

can you please, print the beginning of raw_image and image.jpeg file ? — lenik
– lenik, Commented Jul 4, 2018 at 1:25
I've added the raw_image but upon closer inspection, it looks like the file being created is empty and is 0 bytes. — dadiletta
– dadiletta, Commented Jul 4, 2018 at 15:43
I think you need to pass only the stuff following base64, to decodebytes(). — Mark Setchell
– Mark Setchell, Commented Jul 4, 2018 at 15:48
In case unclear, I mean you should pass /9j.... onwards to decodebytes(), but don't search for /9j because it will be different if you get a PNG file, for example. — Mark Setchell
– Mark Setchell, Commented Jul 4, 2018 at 16:00

lenik · Accepted Answer · 2018-07-04 17:49:09Z

4

I took your data, and decoded it, it looks quite close to the JPEG header I took from the real file (picture below). Don't see any problem, except, you have to start decoding from /9j/4AA... onwards.

>>> a = '/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgMCAgMDAwMEAwMEBQgFBQQEBQoHBwYIDAoMDAsKCwsNDhIQDQ4RDgsLEBYQERMUFRUVDA8XGBYUGBIUFRT/2wBDAQMEBAUEBQkFBQkUDQsNFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBT/wAARCADwAUADASIAAhEBAxEB/8QAHQAAAgIDAQEBAAAAAAAAAAAABQYEBwIDCAEACf/EAEwQAAEDAwMCBAQEAwUFBQQLAAECAxEABAUGEiExQQcTUWEIInGBFDKRoRVCUiOxwdHwJGJyouEJFjOSwhdDgvEmU2ODk7LDxNLU4v/EABsBAAMBAQEBAQAAAAAAAAAA'
>>> base64.b64decode(a)
'\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00C\x00\x03\x02\x02\x03\x02\x02\x03\x03\x03\x03\x04\x03\x03\x04\x05\x08\x05\x05

This is a hex dump from the real JPEG picture of mine.

You have to remove data:image/jpeg;base64,, but don't go beyond that -- this will break the image data.

answered Jul 4, 2018 at 17:49

lenik

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2 Comments

dadiletta Over a year ago

Thanks for your help. Now I get an error on base64.decodebytes(raw_image) : TypeError: expected bytes-like object, not str. I tried to switch to .decodestring() but received the same error. Is my use of raw_image = raw_image.replace("data:image/jpeg;base64,", ''); ruining the data?

lenik Over a year ago

@dadiletta please, carefully read my answer. if you have a string, use base64.b64decode()

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