filters.js

var filters = {
  "grey": function (color, i) {
    var opt = (color.r + color.g + color.b) / 5;
    pix[i+0] = opt;
    pix[i+1] = opt;
    pix[i+2] = opt;
  },
  "black": function (color, i) {
    var opt = (color.r + color.g + color.b) / 3;
    if (opt > 255 / 5) {
      pix[i+0] = 255;
      pix[i+1] = 255;
      pix[i+2] = 255;
    } else if (opt < 255 / 5) {
      pix[i+0] = 0;
      pix[i+1] = 0;
      pix[i+2] = 0;
    }
  },
  "sepia": function (color, i) {
    var idx = i;
    var red = color.r;
    var green = color.g;
    var blue = color.b;
      
    red = (red * 0.393) + (green * 0.769) + (blue * 0.189);
    green = (red * 0.349) + (green * 0.686) + (blue * 0.168);
    blue = (red * 0.272) + (green * 0.534) + (blue * 0.131);
    pix[idx] = (red < 255) ? red : 255;
    pix[idx+1] = (green < 255) ? green : 255;
    pix[idx+2] = (blue < 255) ? blue : 255;
  }
};