Saving base64 encoded image to file

[Mehul Ved]

Hi,

  I am working with Flask where I receive JSON data from an app, which contains base64 JPEG image data. I am using the following code to save it to a file:

    data = json.loads(request.data)

    file = data['entry']['screenshots']

    filename = 'screenshot.jpeg'

    fh = open(filename, 'wb')

    fh.write(file.decode('base64'))

    fh.close()

But, the mimetype for the stored file shows as application/octet-stream. I even tried using base64 module and decodestring as well as b64decode but none of them work.

The data is sent out by https://github.com/nfroidure/BugMeBack and I am trying to capture it in https://github.com/mehulved/bugcatcher

Any clues on what is going wrong? 

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With Regards,
Mehul Ved

[Saket Choudhary]

There seems to be a hack here : https://github.com/sightmachine/simplecv-js/blob/master/webrtc-to-python/server.py. Haven't tested.

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[Vineet Naik]

What mime type does the client set on the request? If it's application/octet-stream then `request.data` may not be the correct way to 

access the input data in Flask. Try reading from the input stream (Don't know how to do this in Flask but probably there would be a method on the request object)

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Vineet Naik

[Dhruv Baldawa]

Just make a FileStorage object out of it and save it, that is what Flask uses for request.files. That should work IMO.

http://werkzeug.pocoo.org/docs/datastructures/#werkzeug.datastructures.FileStorage

Uploading files in Flask

http://flask.pocoo.org/docs/patterns/fileuploads/

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Dhruv Baldawa

(http://www.dhruvb.com)

[Mehul Ved]

On Wed, Jun 19, 2013 at 2:35 PM, Saket Choudhary <sak...@gmail.com> wrote:

There seems to be a hack here : https://github.com/sightmachine/simplecv-js/blob/master/webrtc-to-python/server.py. Haven't tested.

Thanks, let me try that and see if it works. 

[Mehul Ved]

On Wed, Jun 19, 2013 at 2:39 PM, Vineet Naik <nai...@gmail.com> wrote:

What mime type does the client set on the request? If it's application/octet-stream then `request.data` may not be the correct way to 

access the input data in Flask. Try reading from the input stream (Don't know how to do this in Flask but probably there would be a method on the request object)

I receive the data as application/json. The other application sends me a json, inside which I have one of the fields is image.

[Mehul Ved]

On Wed, Jun 19, 2013 at 2:49 PM, Dhruv Baldawa <dhruvb...@gmail.com> wrote:

Just make a FileStorage object out of it and save it, that is what Flask uses for request.files. That should work IMO.

http://werkzeug.pocoo.org/docs/datastructures/#werkzeug.datastructures.FileStorage

Uploading files in Flask

http://flask.pocoo.org/docs/patterns/fileuploads/

I haven't yet checked filestorage but I went through the fileuploads and from what I understand it won't work for me as I am not receiving data in multipart/form-data but as application/json. 

[Vineet Naik]

I think flask unserializes requests with json content type to request.json so you may want to try that instead of request.data

 

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Vineet Naik

[Vineet Naik]

request.json should solve the problem, check this -- http://flask.pocoo.org/docs/api/#flask.Request.json

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Vineet Naik

[Mehul Ved]

On Wed, Jun 19, 2013 at 2:35 PM, Saket Choudhary <sak...@gmail.com> wrote:

There seems to be a hack here : https://github.com/sightmachine/simplecv-js/blob/master/webrtc-to-python/server.py. Haven't tested.

This worked perfectly. I am actually skipping the step of storing on the filesystem now. I will just store the image in the DB, if DB storage is configured. No need to save the file needlessly.

[Mehul Ved]

On Wed, Jun 19, 2013 at 3:30 PM, Vineet Naik <nai...@gmail.com> wrote:

request.json should solve the problem, check this -- http://flask.pocoo.org/docs/api/#flask.Request.json

I remember having tried request.json, which didn't work. But, maybe I was too sleepy and got it wrong. 

The other method has worked for now, but I'll try this as well as my primary reason to choose flask was to learn more about it. 

[Dhruv Baldawa]

This might work I guess:

import cStringIO

from werkzeug.datastructures import FileStorage

decoded_data = request.json['entry']['screenshots'].decode('base64')

file_data = cStringIO.StringIO(decoded_data)

file = FileStorage(file_data, filename='screenshot.jpg', mimetype='application/json')

if file and allowed_file(file.filename):

    filename = secure_filename(file.filename)

    file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))

    return redirect(url_for('uploaded_file',

                            filename=filename))

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Dhruv Baldawa

(http://www.dhruvb.com)

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