yl-gzh/common/tracking.js/src/math/Math.js

(function() {
  /**
   * Math utility.
   * @static
   * @constructor
   */
  tracking.Math = {};

  /**
   * Euclidean distance between two points P(x0, y0) and P(x1, y1).
   * @param {number} x0 Horizontal coordinate of P0.
   * @param {number} y0 Vertical coordinate of P0.
   * @param {number} x1 Horizontal coordinate of P1.
   * @param {number} y1 Vertical coordinate of P1.
   * @return {number} The euclidean distance.
   */
  tracking.Math.distance = function(x0, y0, x1, y1) {
    var dx = x1 - x0;
    var dy = y1 - y0;

    return Math.sqrt(dx * dx + dy * dy);
  };

  /**
   * Calculates the Hamming weight of a string, which is the number of symbols that are
   * different from the zero-symbol of the alphabet used. It is thus
   * equivalent to the Hamming distance from the all-zero string of the same
   * length. For the most typical case, a string of bits, this is the number
   * of 1's in the string.
   *
   * Example:
   *
   * <pre>
   *  Binary string     Hamming weight
   *   11101                 4
   *   11101010              5
   * </pre>
   *
   * @param {number} i Number that holds the binary string to extract the hamming weight.
   * @return {number} The hamming weight.
   */
  tracking.Math.hammingWeight = function(i) {
    i = i - ((i >> 1) & 0x55555555);
    i = (i & 0x33333333) + ((i >> 2) & 0x33333333);

    return ((i + (i >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
  };

  /**
   * Generates a random number between [a, b] interval.
   * @param {number} a
   * @param {number} b
   * @return {number}
   */
  tracking.Math.uniformRandom = function(a, b) {
    return a + Math.random() * (b - a);
  };

  /**
   * Tests if a rectangle intersects with another.
   *
   *  <pre>
   *  x0y0 --------       x2y2 --------
   *      |       |           |       |
   *      -------- x1y1       -------- x3y3
   * </pre>
   *
   * @param {number} x0 Horizontal coordinate of P0.
   * @param {number} y0 Vertical coordinate of P0.
   * @param {number} x1 Horizontal coordinate of P1.
   * @param {number} y1 Vertical coordinate of P1.
   * @param {number} x2 Horizontal coordinate of P2.
   * @param {number} y2 Vertical coordinate of P2.
   * @param {number} x3 Horizontal coordinate of P3.
   * @param {number} y3 Vertical coordinate of P3.
   * @return {boolean}
   */
  tracking.Math.intersectRect = function(x0, y0, x1, y1, x2, y2, x3, y3) {
    return !(x2 > x1 || x3 < x0 || y2 > y1 || y3 < y0);
  };

}());