Complete picture type

The complete definition of the Picture is as follows:(3)

type Unit  -- representation of a printers' points.
type Size   = (Unit,Unit)
type Coord  = (Unit,Unit)
type Angles = (Unit,Unit)
type Translation = (Unit,Unit)

data Picture
 = NullPic | Point | Text String
 | PolyLine [Translation] | Rect Size
 | Arc    Size Angles | Curve Coord Coord Coord
 | Raster Raster      | Pen PenModifier Picture
 | Move Offset Picture
 | Transform Transform Picture
 | Tag Tag Picture
 | Overlay Picture Picture
 | ConstrainOverlay RelSize RelSize Picture Picture 
 | Clip Picture Picture
   deriving (Eq,Text)

data RelSize
 = None | Fixed Which Unit | Prop Which Unit
   deriving (Eq, Text)

data Which = First | Second

type Tag = Int

data Offset 
 = OffDir CompassDirection
 | OffPropX Double
 | OffPropY Double
   deriving (Eq,Text)