Watch folder on server for new images to compress

Question

I have a server and it gets a lot of image uploads. The app uploading the images is based in PHP. However, I want to use Node to watch the upload folder, then run imagemin on any new images.

I was thinking I would use npm packages 'watch' and 'imagemin'. I am not sure how to configure them exactly though or how to have it run all the time.

So far I have the following which I can turn on manually:

var Imagemin = require('imagemin');
var watch = require('watch');
var imagemin = new Imagemin()
  .use(Imagemin.pngquant());
watch.createMonitor('images', function (monitor) {
  monitor.files['images/*.png']
  monitor.on("created", function (file) {
    compressImage(file);
  })
  monitor.on("changed", function (file) {
    compressImage(file);
  });
});

function compressImage(file) {
  var dest, path;
  path = f.split('/');
  path.pop();
  dest = path.join('/');
  imagemin.src(file).dest(dest).run();
}

After a couple of files are added though I get a warning about a possible EventEmitter memory leak detected. 11 listeners added. Use emitter.setMaxListeners() to increase limit and then it stops working.

Is there a better way to do this and how can I run it automatically?

Answer 1

To deal with the recursive firing of the watch function on change, one possible solution is this: Whenever your compression function runs, have it store the filename in a var. On your change listener function, just add

If (file !== lastFile) {
   //do something
}

There is another module that is quite similar you could try, called chokidar.

Has very similar hooks as watch:

watcher.on('add', function(path) { log('File', path, 'has been added'); })
watcher.on('change', function(path) { log('File', path, 'has been changed'); })

Examples here: Watch Files and Directories