Creating a route that returns image metadata (size, mime) as json

• does everything a regular conversion does except calling sharp.metadata on the input stream
• mixes Convert with Route to get existing reader extraction and stream validation behavior

Example usage:

curl http://localhost:3000/image/https%3A%2F%2Fd11xdyzr0div58.cloudfront.net%2Fstatic%2Farchnavbar%2Farchlogo.4fefb38dc270.png
# {"format":"png","width":190,"height":40,"space":"srgb","channels":4,"density":90,"hasProfile":false,"hasAlpha":true}

Implementation

• route url /image/{url}
• input extraction resolves url request param
• overwrites process to simply call sharp.metadata and resolve the object
• overwrites write to simply reply with the extracted metadata object

Route

class ImageMetaRoute extends Convert(Route) {
  constructor(conf, method = 'GET', path = '/image/{url}', description = 'Image metadata conversion') {
    super(conf, method, path, description);
  }

  extractInput(operation) {
    operation.input = url.parse(operation.request.params.url);
    return Promise.resolve(operation.input);
  }

  process() {
    return (stream) =>
      new Promise((resolve, reject) =>
        stream.pipe(sharp().metadata((err, data) => {
          if (err) {
            reject(new InvalidInputError(err));
          } else {
            resolve(data);
          }
        })));
  }

  write(operation){
    return (metadata) => operation.reply(metadata);
  }
}

starting the server

Config.fromEnv().then(config => new Server(config, new AddonLoader(__dirname, {}).load())
    .withProfiles([require('../src/profiles/examples')])
    .withRoutes([new ImageMetaRoute(config)])
    .start()
    .then(server => logger.info(`server running at ${server.hapi.info.uri}`)))

Future ideas

• use color-thief and also extract average color