mind-ar/src/image-target/matching/hamming-distance.js

web augmented reality framework

// Fast computation on number of bit sets
// Ref: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
const compute = (options) => {
  const {v1, v2} = options;
  let d = 0;

  for (let i = 0; i < v1.length; i++) {
    let x = (v1[i] ^ v2[i]) >>> 0;
    d += bitCount(x);
  }
  return d;
}

const bitCount = (v) => {
  var c = v - ((v >> 1) & 0x55555555);
  c = ((c >> 2) & 0x33333333) + (c & 0x33333333);
  c = ((c >> 4) + c) & 0x0F0F0F0F;
  c = ((c >> 8) + c) & 0x00FF00FF;
  c = ((c >> 16) + c) & 0x0000FFFF;
  return c;
}

export {
  compute
};