Pixastic.Actions.weighted_desaturate = {
    each_pixel : function(data, w, h, visit) {
      var w4 = w*4;
      var y = h;
      do {
        var offsetY = (y-1)*w4;
        var x = w;
        do {
          var offset = offsetY + (x-1)*4;
          var newval = visit(data[offset], data[offset+1], data[offset+2], data[offset+3]);
          data[offset]   = newval[0] || data[offset];
          data[offset+1] = newval[1] || data[offset+1];
          data[offset+2] = newval[2] || data[offset+2];
          data[offset+3] = newval[3] || data[offset+3];
        } while (--x);
      } while (--y);
    },
  
    process : function(params) {
      var rweight = params.options.r;
      var gweight = params.options.g;
      var bweight = params.options.b;
      
      var scale = 1 / (rweight + gweight + bweight);
      rweight *= scale;
      gweight *= scale;
      bweight *= scale;
      
      if (Pixastic.Client.hasCanvasImageData()) {
        var data = Pixastic.prepareData(params);
        var rect = params.options.rect;
        var w = rect.width;
        var h = rect.height;
        this.each_pixel(data, w, h, function(r, g, b, a) {
          var brightness = r * rweight + g * gweight + b * bweight;
          return [brightness, brightness, brightness];
        });
        return true;
      }
    },
  
          checkSupport : function() {
                  return Pixastic.Client.hasCanvasImageData();
          }
  }