function Matrix2D(a, b, c, d, tx, ty) {
		this.setValues(a,b,c,d,tx,ty);
		
	// public properties:
		// assigned in the setValues method.
		/**
		 * Position (0, 0) in a 3x3 affine transformation matrix.
		 * @property a
		 * @type Number
		 **/
	
		/**
		 * Position (0, 1) in a 3x3 affine transformation matrix.
		 * @property b
		 * @type Number
		 **/
	
		/**
		 * Position (1, 0) in a 3x3 affine transformation matrix.
		 * @property c
		 * @type Number
		 **/
	
		/**
		 * Position (1, 1) in a 3x3 affine transformation matrix.
		 * @property d
		 * @type Number
		 **/
	
		/**
		 * Position (2, 0) in a 3x3 affine transformation matrix.
		 * @property tx
		 * @type Number
		 **/
	
		/**
		 * Position (2, 1) in a 3x3 affine transformation matrix.
		 * @property ty
		 * @type Number
		 **/
	}
Represents an affine transformation matrix, and provides tools for constructing and concatenating matrices.

This matrix can be visualized as:

	[ a  c  tx
	  b  d  ty
	  0  0  1  ]

Note the locations of b and c.

@class Matrix2D
@param {Number} [a=1] Specifies the a property for the new matrix.
@param {Number} [b=0] Specifies the b property for the new matrix.
@param {Number} [c=0] Specifies the c property for the new matrix.
@param {Number} [d=1] Specifies the d property for the new matrix.
@param {Number} [tx=0] Specifies the tx property for the new matrix.
@param {Number} [ty=0] Specifies the ty property for the new matrix.
@constructor