When an application scales an object by using the scaling transformation,
the matrix element M11 contains the horizontal scaling component (Sx), and
the matrix element M22 contains the vertical scaling component
(Sy).
┌ ┐
│ Sx 0 0 │
[ x' y' 1 ] = [ x y 1 ] * │ 0 Sy 0 │
│ 0 0 1 │
└ ┘
If the matrix element M11 contains a negative horizontal reflection component (-Sx), it causes reflection about the y-axis. If the matrix element M22 contains a negative vertical reflection component (-Sy) it causes reflection about the x-axis.