What is the simplest code to serve a small image (jpg) from cloud storage to a webpage (Google 'Hello World' app)?

Question

JPG is uploaded to a bucket https://storage.googleapis.com/ .... Should I use blobs or get_serving_url API?

...I have tried a couple of different methods but keep getting an error. Here is the Hello World example:

import webapp2


class MainPage(webapp2.RequestHandler):
    def get(self):
        self.response.headers['Content-Type'] = 'text/plain'
        self.response.write('Hello, World, Hello!')

app = webapp2.WSGIApplication([
    ('/', MainPage),
], debug=True)

Answer 1

If you want to use App Engine standard, you'll need to complete a few steps first:

1. Activate a Cloud Storage bucket
2. Download the cloudstorage client library
3. Install the client library as a third-party dependency

Then you can take the quickstart project for App Engine Standard Environment and modify the main.py file to look like:

import webapp2
import cloudstorage as gcs


class MainPage(webapp2.RequestHandler):
    def get(self):
        gcs_file = gcs.open('/your-bucket-name/your-image.jpg')
        contents = gcs_file.read()
        gcs_file.close()
        self.response.write(contents)
        self.response.headers['Content-Type'] = 'image/jpeg'


app = webapp2.WSGIApplication([('/', MainPage)], debug=True)

When you're done you should have a directory structure with the following structure:

.
├── app.yaml
├── appengine_config.py
├── lib
│   └── cloudstorage
│       ├── __init__.py
│       ├── api_utils.py
│       ├── cloudstorage_api.py
│       ├── common.py
│       ├── errors.py
│       ├── rest_api.py
│       ├── storage_api.py
│       └── test_utils.py
└── main.py

And you can deploy it with:

$ gcloud app deploy

---

That said, you also don't really need a full-blown App Engine instance to serve a single image -- you could also just do it with a Google Cloud Function like so:

In requirements.txt :

google-cloud-storage

In main.py :

from google.cloud import storage
from flask import make_response

client = storage.Client()
bucket = client.get_bucket('your-bucket-name')
blob = bucket.get_blob('your-image.jpg').download_as_string()

def serve_image(request):
    return make_response((blob, {'Content-Type': 'image/jpeg'}))

And deploy it with:

$ gcloud beta functions deploy serve_image --runtime python37 --trigger-http