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
import Control.Monad.Writer

import Graphics.PDF.LowLevel.Serializer
import Data.Monoid

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






-- | Apply a transformation matrix to the current coordinate frame
applyMatrix :: Matrix -> Draw ()
applyMatrix m@(Matrix a b c d e f)  = do
    multiplyCurrentMatrixWith m
    tell . mconcat $[ serialize '\n'
                    , toPDF a
                    , serialize ' '
                    , toPDF b
                    , serialize ' '
                    , toPDF c
                    , serialize ' '
                    , toPDF d
                    , serialize ' '
                    , toPDF e
                    , serialize ' '
                    , toPDF f
                    , serialize " 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