How to get snapshoutUri and finally snapshot from ONVIF camera

gistfile1.txt

/* this is a partial gist */
const Promise = require('bluebird')
const axios = require('axios')
const Camera = require('onvif').Cam

class OnvifManager {
  //...
  this.cameras = {}
  //...
  
  readCamerasFromDatabase () {
  //...
  let onvif = // code to read from database
  
  let options = {}
  options.hostname = onvif.address
  options.username = onvif.login
  options.password = onvif.password
  if (onvif.port && onvif.port !== 80) {
    options.port = onvif.port
  }
  
  let camera = new Camera(options, error => {
    camera.onvif = onvif
    
    // assign to list of cameras
    this.cameras[onvif.id] = camera
    
    if (error === null) {
      camera.getSnapshotUri({}, (error, data, xml) => {
        if (error) {
          console.error(`Cannot get snapshot URI for ${camera.onvif.name}/${camera.onvif.address}`)
        }
        else {
          camera.snapshotUri = data
        }
      })
    }
  }

  // call this function whenever a snapshot from the onvif camera is desired
  commandFetchSnapshot (id) {
    return new Promise((resolve, reject) => {
      let camera = this.cameras[id]
      if (!camera) {
        let results = {
          message: 'Not Found',
          status: 404
        }
        reject(new Error(results))
      }
      else {
        // check that we have a snapshotUri attached to this camera
        if ('snapshotUri' in camera) {
          let snapshotUri = camera.snapshotUri.uri

          // using axios.get with options { responseType: 'arraybuffer' }
          // did not work at all. The data returned was transformed somehow.
          // This way works!
          axios.request({
            responseType: 'arraybuffer',
            url: snapshotUri,
            method: 'get',
            headers: {
              'Content-Type': 'image/*'
            },
            auth: {
              username: camera.username,
              password: camera.password
            }
          })
            .then((results) => {
              let mimeType = results.headers['content-type']
              // using nodejs Buffer to encode the inary to base64
              let b64encoded = Buffer.from(results.data, 'binary').toString('base64')
              let image = 'data:' + mimeType + ';base64,' + b64encoded
              let data = {
                mimeType: mimeType,
                image: image
              }
              // uncomment to write image to disk for testing
              // const outputFilename = '/tmp/testfile.jpg'
              // fs.writeFileSync(outputFilename, results.data)
              resolve(data)
            })
            .catch(error => {
              console.error('commandFetchSnapshot error', error)
              let results = {
                message: 'fetchSnapshot error',
                status: 250,
                error: error
              }
              reject(new Error(results))
            })
        }
        else {
          let results = {
            message: 'Unknown in commandFetchSnapshot',
            status: 250
          }
          reject(new Error(results))
        }
      }
    })
  }
}
  
  

Axios couldn't handle working with Axis camera authentication because it uses Realm Digest. I have since changed my code to use the 'request' package.

New gist here: https://gist.github.com/hawkeye64/e67cb5aae8f46d9c94ea2c9a4bb9247b