geom.go
func (g *GeoM) Add(other GeoM) {
	g.a_1 += other.a_1
	g.b += other.b
	g.c += other.c
	g.d_1 += other.d_1
	g.tx += other.tx
	g.ty += other.ty
}
func (g *GeoM) Add(other GeoM) {
	g.a_1 += other.a_1
	g.b += other.b
	g.c += other.c
	g.d_1 += other.d_1
	g.tx += other.tx
	g.ty += other.ty
}
// Add is deprecated as of 1.5.0-alpha.
// Note that this doesn't make sense as an operation for affine matrices.