worker.js

if (this.Editor) {
  Editor.Worker = function(editor, data, callback) {
    if (!editor.workers) {
      editor.workers = [];
      editor.idleWorkers = [];
      editor.workerQueue = [];
    }

    var worker = editor.idleWorkers.pop()
    if (!worker) {
      if (editor.workers.length < Editor.Worker.max) {
        var worker = new Worker('worker.images.js');
        editor.workers.push(worker);
      } else {
        editor.workerQueue.push(data, callback)
      }
    }
    if (worker)
      Editor.Worker.process(editor, worker, data, callback)
    return editor.worker;
  }
  Editor.Worker.max  = 2;

  Editor.Worker.process = function(editor, worker, data, callback) {
    var listener = function(e) {
      callback.call(editor, e.data)

      worker.removeEventListener('message', listener);

      var cb = editor.workerQueue.pop()
      if (cb) {
        Editor.Worker.process(editor, worker, editor.workerQueue.pop(), cb)
      } else {
        editor.idleWorkers.push(worker)
        clearTimeout(editor.killWorkers)
        editor.killWorkers = setTimeout(function() {
          editor.idleWorkers = editor.idleWorkers.filter(function(worker, index) {
            if (index > 0) {
              var i = editor.workers.indexOf(worker)
              if (i > -1) 
                editor.workers.splice(i, 1)
              worker.terminate()
            } else {
              return true;
            }
          });
        }, 5000)
      }
    };
    worker.addEventListener('message', listener);
    worker.postMessage(data)
  }
} else {
  self.addEventListener('message', function(e) {
    var data = e.data;

    var width = data.width;
    var height = data.height;
    var ratio = width / height;

    // Resize image if necessary 
    if (width > 1440 || height > 900) {
      width = Math.min(1440, width)
      height = Math.floor(width / ratio);
      if (height > 900) {
        width = Math.floor(width / (height / 900));
        height = 900
      }
      console.time('Image: resize ' + data.width + 'x' + data.height + ' to ' + width + 'x' + height);
      var resized = {
        width: width,
        height: height,
        data: resizeImage({
          src: data.data,
          width: data.width,
          height: data.height,
          toWidth: width,
          toHeight: height,
          dest: new Uint8ClampedArray(width * height * 4),
          quality: 3
        })
      }
      console.timeEnd('Image: resize ' + data.width + 'x' + data.height + ' to ' + width + 'x' + height);
      var unsharpAmount = 20;
      console.time('Image: unsharp after resize ' + width + 'x' + height + ' by ' + unsharpAmount)
      unsharpImage(resized.data, width, height, unsharpAmount, 0.5, 3);
      console.timeEnd('Image: unsharp after resize ' + width + 'x' + height + ' by ' + unsharpAmount)
    }

    console.time('Image: quantize ' + width + 'x' + height);
    var palette = Palette(resized || data)
    console.timeEnd('Image: quantize ' + width + 'x' + height);

    // Analyze image to pick best square crop

    console.time('Image: crop to square ' + width + 'x' + height);
    smartcrop.crop(resized || data, {
      imageOperations: IO,
      width: Math.min(data.width, data.height),
      height: Math.min(data.height, data.width)
    }).then(function(result) {
      console.timeEnd('Image: crop to square ' + width + 'x' + height);
      // send data to main thread to put unto canvas
      if (resized) {
        postMessage({
          palette: palette.toString(),
          square: result.topCrop,
          resized: resized
        }, [resized.data.buffer]);
      } else {
        postMessage({
          palette: palette.toString(),
          square: result.topCrop
        });

      }

    })

  }, false);


  var IO = {
    // Takes imageInput as argument
    // returns an object which has at least
    // {width: n, height: n}
    open: function(image) {
      return smartcrop.Promise.resolve(image);
    },
    // Takes an image (as returned by open), and changes it's size by resampling
    resample: function(image, width, height) {
      return Promise.resolve(image).then(function(image) {
        var c = canvasFactory(~~width, ~~height);
        var ctx = c.getContext('2d');

        ctx.drawImage(image, 0, 0, image.width, image.height, 0, 0, c.width, c.height);
        return smartcrop.Promise.resolve(c);
      });
    },
    getData: function(image) {
      return Promise.resolve(image).then(function(c) {
        return image
      });
    },
  }


}