See https://ithoughthecamewithyou.com/post/get-an-email-when-your-security-camera-sees-something-new-apps-script--cloud-vision

CloudVision.gs

var OAuthCreds = {
  "type": "service_account",
  //...
};

var SendEmailTo = '';
var MonitorImageUrl = '';



function main() {
  var timestamp = Date.now().toString();
  var scriptProperties = PropertiesService.getScriptProperties();
  var currentProps = scriptProperties.getProperties();
  
  Logger.log('Grabbing a frame');
  var url = MonitorImageUrl + '&cb=' + timestamp;
  var response = UrlFetchApp.fetch(url);
  var image = response.getBlob();
  image.setName('image.jpg');
  var bytes = image.getBytes();
  var encodedImage = Utilities.base64EncodeWebSafe(bytes);
  
  Logger.log('Calling cloud vision');
  var service = getService();
  if (service.hasAccess()) {
    
    var request = {
      "requests":[
        {
          "image":{
            "content": encodedImage
          },
          "features":[
            {
              "type": "LABEL_DETECTION",
              "maxResults":50
            }
          ]
        }
      ]
    }
    
    var annotateUrl = 'https://vision.googleapis.com/v1/images:annotate';
    var annotateResponse = UrlFetchApp.fetch(annotateUrl, {
      "headers": {
        Authorization: 'Bearer ' + service.getAccessToken()
      },
      "method" : "post",
      "contentType" : "application/json",
      "payload" : JSON.stringify(request, null, 2)
    });
    var json = JSON.parse(annotateResponse.getContentText());
    
    var anythingNew = false;
    var newText = '';
    
    for (var l = 0; l < json.responses[0].labelAnnotations.length; l++) {
      var description = json.responses[0].labelAnnotations[l].description;
      var score = json.responses[0].labelAnnotations[l].score;
      
      if (!(description in currentProps)) {
        Logger.log('Found new feature: ' + description);
        scriptProperties.setProperty(description, score);
        anythingNew = true;
        newText += 'Found: ' + description + ' (score: ' + score + ')\r\n';
      }
    }
    
    if (anythingNew) {
      MailApp.sendEmail(SendEmailTo, 'Found something new on the webcam ' + new Date(), newText, { 
        attachments: [image] 
      });
    }
    
  } else {
    Logger.log(service.getLastError());
  }
}

// modified from https://github.com/googlesamples/apps-script-oauth2/blob/master/samples/GoogleServiceAccount.gs#L50 below...
function getService() {
  return OAuth2.createService('CloudVision')
      // Set the endpoint URL.
      .setTokenUrl(OAuthCreds.token_uri)

      // Set the private key and issuer.
      .setPrivateKey(OAuthCreds.private_key)
      .setIssuer(OAuthCreds.client_email)

      // Set the name of the user to impersonate. This will only work for
      // Google Apps for Work/EDU accounts whose admin has setup domain-wide
      // delegation:
      // https://developers.google.com/identity/protocols/OAuth2ServiceAccount#delegatingauthority
     // .setSubject(USER_EMAIL)

      // Set the property store where authorized tokens should be persisted.
      .setPropertyStore(PropertiesService.getScriptProperties())

      // Set the scope. This must match one of the scopes configured during the
      // setup of domain-wide delegation.
      .setScope('https://www.googleapis.com/auth/cloud-platform');
}

function reset() {
  var service = getService();
  service.reset();
}