text: // Last updated November 2011
  // By Simon Sarris
  // www.simonsarris.com
  // sarris@acm.org
  //
  // Free to use and distribute at will
  // So long as you are nice to people, etc
  
  // Simple class for keeping track of the current transformation matrix
  
  // For instance:
  //    var t = new Transform();
  //    t.rotate(5);
  //    var m = t.m;
  //    ctx.setTransform(m[0], m[1], m[2], m[3], m[4], m[5]);
  
  // Is equivalent to:
  //    ctx.rotate(5);
  
  // But now you can retrieve it :)
  
  // Remember that this does not account for any CSS transforms applied to the canvas
  
  function Transform() {
    this.reset();
  }
  
  Transform.prototype.reset = function() {
    this.m = [1,0,0,1,0,0];
  };
  
  Transform.prototype.multiply = function(matrix) {
    var m11 = this.m[0] * matrix.m[0] + this.m[2] * matrix.m[1];
    var m12 = this.m[1] * matrix.m[0] + this.m[3] * matrix.m[1];
  
    var m21 = this.m[0] * matrix.m[2] + this.m[2] * matrix.m[3];
    var m22 = this.m[1] * matrix.m[2] + this.m[3] * matrix.m[3];
  
    var dx = this.m[0] * matrix.m[4] + this.m[2] * matrix.m[5] + this.m[4];
    var dy = this.m[1] * matrix.m[4] + this.m[3] * matrix.m[5] + this.m[5];
  
    this.m[0] = m11;
    this.m[1] = m12;
    this.m[2] = m21;
    this.m[3] = m22;
    this.m[4] = dx;
    this.m[5] = dy;
  };
  
  Transform.prototype.invert = function() {
    var d = 1 / (this.m[0] * this.m[3] - this.m[1] * this.m[2]);
    var m0 = this.m[3] * d;
    var m1 = -this.m[1] * d;
    var m2 = -this.m[2] * d;
    var m3 = this.m[0] * d;
    var m4 = d * (this.m[2] * this.m[5] - this.m[3] * this.m[4]);
    var m5 = d * (this.m[1] * this.m[4] - this.m[0] * this.m[5]);
    this.m[0] = m0;
    this.m[1] = m1;
    this.m[2] = m2;
    this.m[3] = m3;
    this.m[4] = m4;
    this.m[5] = m5;
  };
  
  Transform.prototype.rotate = function(rad) {
    var c = Math.cos(rad);
    var s = Math.sin(rad);
    var m11 = this.m[0] * c + this.m[2] * s;
    var m12 = this.m[1] * c + this.m[3] * s;
    var m21 = this.m[0] * -s + this.m[2] * c;
    var m22 = this.m[1] * -s + this.m[3] * c;
    this.m[0] = m11;
    this.m[1] = m12;
    this.m[2] = m21;
    this.m[3] = m22;
  };
  
  Transform.prototype.translate = function(x, y) {
    this.m[4] += this.m[0] * x + this.m[2] * y;
    this.m[5] += this.m[1] * x + this.m[3] * y;
  };
  
  Transform.prototype.scale = function(sx, sy) {
    this.m[0] *= sx;
    this.m[1] *= sx;
    this.m[2] *= sy;
    this.m[3] *= sy;
  };
  
  Transform.prototype.transformPoint = function(px, py) {
    var x = px;
    var y = py;
    px = x * this.m[0] + y * this.m[2] + this.m[4];
    py = x * this.m[1] + y * this.m[3] + this.m[5];
    return [px, py];
  };