Coordinates.hs

---------------------------------------------------------
-- |
-- Copyright   : (c) alpha 2007
-- License     : BSD-style
--
-- Maintainer  : misc@NOSPAMalpheccar.org
-- Stability   : experimental
-- Portability : portable
--
-- Coordinates for a PDF document
---------------------------------------------------------

module Graphics.PDF.Coordinates(
    -- * Geometry
    -- ** Types
      Angle(..)
    , Matrix(..)
    -- ** Transformations
    , rotate, translate, scale, identity
    -- ** Frame of reference operators
    , applyMatrix
    )
    where

import Graphics.PDF.LowLevel.Types
import Graphics.PDF.Draw

-- | Angle 
data Angle = Degree PDFFloat -- ^ Angle in degrees
           | Radian PDFFloat -- ^ Angle in radians

-- | A transformation matrix. An affine transformation a b c d e f
--
-- @
-- a b e
-- c d f
-- 0 0 1
-- @
       
data Matrix = Matrix !PDFFloat !PDFFloat !PDFFloat !PDFFloat !PDFFloat !PDFFloat deriving (Eq)

-- | Identity matrix
identity :: Matrix
identity = Matrix 1.0 0 0 1.0 0 0

instance Show Matrix where
  show (Matrix ma mb mc md me mf) = "Matrix " ++ (unwords [(show ma),(show mb),(show mc),(show md),(show me),(show mf)])

instance Num Matrix where
    --  Matrix addition
    (+) (Matrix ma mb mc md me mf ) (Matrix na nb nc nd ne nf) = 
         Matrix (ma+na)  (mb+nb)  (mc+nc)  (md+nd)  (me+ne)  (mf+nf)
    (*) (Matrix ma mb mc md me mf) (Matrix na nb nc nd ne nf) = 
         Matrix (ma*na+mb*nc)  (ma*nb + mb*nd )  (mc*na+md*nc)  (mc*nb +md*nd)  (me*na+mf*nc+ne)  (me*nb+mf*nd+nf)
    negate (Matrix ma mb mc md me mf )  =
         Matrix (-ma)  (-mb)  (-mc)  (-md)  (-me)  (-mf)
    abs m = m
    signum _ = identity
    fromInteger i = Matrix r 0 0 r  0  0
                   where
                    r = fromInteger i


-- | Apply a transformation matrix to the current coordinate frame
applyMatrix :: Matrix -> Draw ()
applyMatrix (Matrix a b c d e f)  = 
    writeCmd $ "\n" ++ show (a) ++ " " ++ show (b) ++ " " ++ show (c) ++ " " ++ show (d) ++ " " ++ show (e) ++ " " ++ show (f) ++ " cm"

-- | Rotation matrix
rotate :: Angle -- ^ Rotation angle
       -> Matrix
rotate r = Matrix ( (cos radian))  ( (sin radian))  (- ( (sin radian)))  ( (cos radian))  0  0
           where
             radian = case r of
                      Degree angle -> angle / 180 *  pi
                      Radian angle -> angle


-- | Translation matrix            
translate :: PDFFloat -- ^ Horizontal translation
          -> PDFFloat -- ^ Vertical translation
          -> Matrix
translate tx ty  = Matrix  1  0  0  1  tx ty


-- | Scaling matrix          
scale :: PDFFloat  -- ^ Horizontal scaling
      -> PDFFloat  -- ^ Horizontal scaling
      -> Matrix
scale sx sy  = Matrix sx 0 0 sy 0 0