Feature Request: Hexadecimal

[marcoas]

(Translated by Google)

Hi
It did not even save more space if you'll keep the numbers in hexadecimal format ?

[igorti]

It probably would. Could you make a pull request with an example that illustrates that it's a more efficient format?

[marcoas]

(Translated by Google)

Sorry, I do not use GIT . I can not send a 'Pull Request' .
I only copied the code and used it .

Anyway , I send my modified code .

Originally I thought to save the values ​​in Hexadecimal , to save a few bytes. But then , I see that 36 is the maximum possible value , to transform into Javascript, it says in http://www.w3schools.com/jsref/jsref_tostring_number.asp

As an example of the savings, I mention that I have a file with 5 polygons . The file has more than 7200 coordinates. The size of the original file is ~ 212KB and finished ~ 82kb ( ~ 39 % )

These are the new / modified functions:

function GeojsonMinifier() {
  this.precision = 7;
  this.factor = 36;
}

GeojsonMinifier.prototype.encodeGeometry = function(coordinates) {
  var minified = [];
  var previous = coordinates[0];
  minified.push(previous[0], previous[1]);

  for (var i = 1; i < coordinates.length; i++) {
    minified.push( this.zigzag(coordinates[i][0], previous[0]) );
    minified.push( this.zigzag(coordinates[i][1], previous[1]) );
    previous = coordinates[i];
  }

  return minified;
}

GeojsonMinifier.prototype.decodeGeometry = function(coordinates) {
  var decodedGeometry = [];
  var previous = [];
  previous.push(coordinates[0], coordinates[1]);
  decodedGeometry.push(previous);

  for (var i = 2; i < coordinates.length; i+=2) {
    var current = [ parseInt(coordinates[i],this.factor), parseInt(coordinates[i+1],this.factor) ];
    var decoded = [];

    decoded[0] = this.unZigzag(current[0], previous[0] );
    decoded[1] = this.unZigzag(current[1], previous[1] );
    decodedGeometry.push(decoded);
    previous = decoded;
  }

  return decodedGeometry;
}

GeojsonMinifier.prototype.zigzag = function( n, previous ) {
    var current = this.toWholeNumber( n );
    var delta = current - this.toWholeNumber(previous);
    zigzag = (delta << 1) ^ (delta >> 31);
    return zigzag.toString(this.factor);
}

GeojsonMinifier.prototype.unZigzag = function( n, previous ) {
    var zigzag = (n >>> 1) ^ -(n & 1);
    var delta = this.toWholeNumber(previous) + zigzag;
    return this.fromWholeNumber(delta);
}