code: func NewSprite(pic Picture, frame Rect) *Sprite {
  	tri := MakeTrianglesData(6)
  	s := &Sprite{
  		tri: tri,
  		d:   Drawer{Triangles: tri},
  	}
  	s.matrix = IM
  	s.mask = Alpha(1)
  	s.Set(pic, frame)
  	return s
  }
docs: // NewSprite creates a Sprite from the supplied frame of a Picture.