Uploading Images via APIs in the Open Event Server

APIs help us to send and receive data in some particular data format that can then be used individually or integrated with a frontend UI. In our case, the entire API server is used to manage all the requests from the frontend and send back the necessary response. Usually, the application is to send simple form data which is then stored into the backend database and a valid jsonapi response is shown. However other than normal text, url, datetime data one very important data is media files, in our case event images, user images, slides, etc. In this blog, we will particularly deal with how we can upload images in the server using API.

Sending Data

Firstly, we need to decide how do we send the data in the post request of the API. So we are sending a base64 encoded string representing the image along with the image extension appended to it, for example, data:image/png;base64,iVBORw0KGgoAAAANS. This is a widely used format for showing images over the web. So when we send a POST request we send a json encoded body like:

{
    "data": "data:image/png;base64,iVBORw0KGgoAAAANS"
}

Converting Base64 Data to Image

There are 2 parts of the data in the string that we receive. The first part basically tells us the format of the image(.gif in this case) and string encoding(base64 in this case), the second part gives us the encoded string. So, from the first part, we extract the file extension for the image file to be created. We use uuid.uuid4() for a random filename.

filename = '{}.{}'.format(str(uuid.uuid4()).data.split(";")[0].split("/")[1])

Now to write the base64 encoded string as an image file, we first need to get only the encoded string part from the data and then decode it. We use string decode function of python for the decoding purpose. Then we write the data to the image file and save it.

file.write(data.split(",")[1].decode("base64")

API Response

Finally using whatever logic you are using for serving your static files, you generate the static file path for the image saved. And then create another json encoded response which returns you the url for the saved image in the server.

{
    "url": "https://xyz.storage.com/asd/fgh/hjk/1233456.png"
}

And there you have your image uploaded and served.

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PIL to convert type and quality of image

Image upload is an important part of the server. The images can be in different formats and after applying certain javascript modifications, they can be changed to different formats. For example, when an image is uploaded after cropping in open event organizer server, it is saved in PNG format. But PNG is more than 5 times larger than JPEG image. So when we upload a 150KB image, the image finally reaching the server is around 1MB which is huge. So we need to decide in the server which image format to select in different cases and how to convert them.

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How can you get an access to Instagram API?

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First of all you need to know that Instagram API uses OAuth 2.0 protocol. OAuth 2.0 provides a specific authorization flow for web apps, desktop apps and mobile apps. Instagram requires authentication before getting information from their API, but don’t be afraid it’s very simple.

Pre Requirements:

  • Created account in Instagram
  • Registered Client(You can create your own client here)

Instagram Developer Documentation.png

Requirements:

CLIENT_ID -79e1a142dbeabd57a3308c52ad43e31d
CLIENT_SECRET -34a6834081c44c20bd11e0a112a6adg1
REDIRECT_URI - http://127.0.0.1:8001/iCallback

You can get above information from https://www.instagram.com/developer/clients/manage/

CODE - You need to open page https://api.instagram.com/oauth/authorize/?client_id=CLIENT-ID&redirect_uri=REDIRECT-URI&response_type=code
https://api.instagram.com/oauth/authorize/?client_id=79e1a142dbeabd57a3308c52ad43e31d&redirect_uri=http://127.0.0.1:8001/iCallback&response_type=code

You will be redirected to

http://your-redirect-uri?code=CODE

In my case it looks like this:

http://127.0.0.1:8001/iCallback?code=2e122f3d76e8125b8b4982f16ed623c2

Now we have all information to get access token!

 curl -F 'client_id=CLIENT_ID'  
      -F 'client_secret=CLIENT_SECRET' 
      -F 'grant_type=authorization_code'  
      -F 'redirect_uri=REDIRECT_URI' 
      -F 'code=CODE'  https://api.instagram.com/oauth/access_token

if everything is ok you should receive

 { "access_token": "fb2e77d.47a0479900504cb3ab4a1f626d174d2d",
   "user": { "id": "1574083",
   "username": "rafal_kowalski",
   "full_name": "Rafal Kowalski",
   "profile_picture": "..." } } 

In Open Event we used it to get all media from instagram – to use it  as for example a background in an event details’ page

curl 'https://api.instagram.com/v1/users/self/media/recent/?access_token=ACCESS_TOKEN'

 

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