class Matrix {

    public float getDeterminant(){
        // ref http://en.wikipedia.org/wiki/Determinant   
        // note that in PDF, I13 and I23 are always 0 and I33 is always 1
        // so this could be simplified/faster
        return    vals[I11] * vals[I22] * vals[I33] 
                + vals[I12] * vals[I23] * vals[I31]
                + vals[I13] * vals[I21] * vals[I32]
                - vals[I11] * vals[I23] * vals[I32]
                - vals[I12] * vals[I21] * vals[I33]
                - vals[I13] * vals[I22] * vals[I31];
    }

    public  Matrix();
    public  Matrix(float tx, float ty);
    public  Matrix(float a, float b, float c, float d, float e, float f);

}