func flop(image *vips.Image) error { return image.Flip(vips.DirectionHorizontal) }
func transverse(image *vips.Image) error { if err := image.Flip(vips.DirectionVertical); err != nil { return err } return image.Rot(vips.Angle270) }
func flip(image *vips.Image) error { return image.Flip(vips.DirectionVertical) }