imaginator

Construct images on the fly via a simple URL!

Install

You'll need to install Cairo as it currently can't be installed automatically with npm... If you want pdf support, install with --enable-pdf=yes. Same for --enable-svg=yes

Usage

var middleware = imaginate(options)

• options (object) - Coming soon
• returns (function) middleware - Responds to requests with images created using the info provided in the query string

const imaginage = require('imaginate')

const middleware = imaginate()
app.use('/images', middleware)

The returned middlware expects the following query string parameters to be provided with each request (preferably via urlinate) and responds with the created image.

• input {string} - URL of original image to download a inject in a canvas context.
• use {array} - List of context transforms to apply (package name or url), in order. Each item should be an array with two items, the first being a url specifying where to get the transform from, the second being an options object specifying the options to use for that transform (see transform docs).

Transforms

If the transform is a URL, imaginate will execute the file at that URL

Whitelisting transforms

I hope that reading this gave you the chills. Are they really allowing people to execute arbitrary code on their machines via a simple GET request? This is where the whitelisting feature comes in.

• GET /whitelist responds with the whitelist as JSON
• POST /whitelist allows you to update the whitelist and is subject to basic authentication (username: admin, password: process.env.IMAGINATOR_PASS.

When transforms throw

Transforms are encouraged to throw really nice errors as these are passed along as-is to the user

Imaginator URLs

Supposing there is an imaginator running at http://imaginator.io,

var urlinate = require('urlinate')
var url = urlinate('http://imaginator.io', {
  input: 'http://wtv.com/img.jpg',
  use: [
    [ 'http://npmjs.com/package/ctx-resize', {
      width: 900,
      height: 600
    }]
  ]
})

Notice the helper function, urlinate.

Then use the URL like any image URL:

HTML

<img src="IMAGINATOR_URL">

CSS

body {
  background: url('IMAGINATOR_URL');
}

JavaScript (browser)

img_DOM_Node.src = 'IMAGINATOR_URL'
DOM_Node.style.background = "url('IMAGINATOR_URL')"

Node.js

http.get('IMAGINATOR_URL', ...)

npm start

Launches a production-ready http server using this middleware.

Required environment variables

Whitelist

This server also provides a /whitelist route which you can GET or POST json to. This whitelist is a package.json['dependencies']-style json object listing the allowed canvas transforms. This whitelist will be saved as a json file on S3 so that it can persist after a crash or restart. To authenticate with S3, the imaginator expects the following environment variables to be set:

• IMAGINATOR_AWS_ACCESS_KEY_ID
• IMAGINATOR_AWS_SECRET_ACCESS_KEY
• IMAGINATOR_BUCKET

It also expects the IAM user to be associated to a policy giving it read and write permissions on the correct bucket and expects a file called whitelist.json to exist within the specified bucket and to be valid JSON (should look like the dependencies object in a package.json file). For more, have a fun time getting lost in the (poor but plentiful) AWS documentation.

Finally, modifying the whitelist requires basic Authentication. The username is always admin, but the password is determined by the value of the IMAGINATOR_PASS environment variable.

• IMAGINATOR_PASS

Warnings and Alerts

In production (NODE_ENV === 'production'), this server will send all warnings and alerts to Slack as configured by:

• IMAGINATOR_SLACK_TOKENS
• IMAGINATOR_SLACK_CHANNEL

Deployment

Docker

1. Build the image

docker build -t imaginator .

2. Launch the image

docker run --rm -ti -p 3000:3000\
  -e IMAGINATOR_PASS=$IMAGINATOR_PASS\
  -e IMAGINATOR_SLACK_CHANNEL=$IMAGINATOR_SLACK_CHANNEL\
  -e IMAGINATOR_SLACK_TOKENS=$IMAGINATOR_SLACK_TOKENS\
  -e IMAGINATOR_AWS_ACCESS_KEY_ID=$IMAGINATOR_AWS_ACCESS_KEY_ID\
  -e IMAGINATOR_AWS_SECRET_ACCESS_KEY=$IMAGINATOR_AWS_SECRET_ACCESS_KEY\
  -e IMAGINATOR_BUCKET=$IMAGINATOR_BUCKET\
  imaginator

nowjs

now\
  -e IMAGINATOR_PASS=$IMAGINATOR_PASS\
  -e IMAGINATOR_SLACK_CHANNEL=$IMAGINATOR_SLACK_CHANNEL\
  -e IMAGINATOR_SLACK_TOKENS=$IMAGINATOR_SLACK_TOKENS\
  -e IMAGINATOR_AWS_ACCESS_KEY_ID=$IMAGINATOR_AWS_ACCESS_KEY_ID\
  -e IMAGINATOR_AWS_SECRET_ACCESS_KEY=$IMAGINATOR_AWS_SECRET_ACCESS_KEY\
  -e IMAGINATOR_BUCKET=$IMAGINATOR_BUCKET

...then press 2 for Dockerfile (see nowjs.org)