geom.go
func (g *GeoM) Apply(x, y float64) (float64, float64) {
	x2, y2 := g.apply32(float32(x), float32(y))
	return float64(x2), float64(y2)
}
func (g *GeoM) Apply(x, y float64) (float64, float64) {
	x2, y2 := g.apply32(float32(x), float32(y))
	return float64(x2), float64(y2)
}
// Apply pre-multiplies a vector (x, y, 1) by the matrix.
// In other words, Apply calculates GeoM * (x, y, 1)^T.
// The return value is x and y values of the result vector.