code: function ImagePHash(size, smallerSize) {
    this.size = this.size || size;
    this.smallerSize = this.smallerSize || smallerSize;
    initCoefficients(this.size);
  }
docs: https://code.google.com/p/ironchef-team21/source/browse/ironchef_team21/src/ImagePHash.java /*
  pHash-like image hash.
  Author: Elliot Shepherd (elliot@jarofworms.com
  Based On: http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html