public override bool Equals(object obj)
{
Matrix m = obj as Matrix;
if (m != null) {
var o = m.transform;
var t = transform;
return (o.x0 == t.x0 && o.y0 == t.y0 &&
o.xx == t.xx && o.yy == t.yy &&
o.xy == t.xy && o.yx == t.yx);
} else
return false;
}