Color.hs

-- | Functions used to control the colors in a PDF document

module Graphics.PDF.Color 
 (-- * Colors
  -- ** Data types
  Color(..)
  -- ** Operators
  , strokeColor,fillColor,rgbSpace, setAlpha,resetAlpha
 )
 where
 
import Graphics.PDF.LowLevel
import Text.Printf
  
-- | Color data type
data Color = Rgb Float Float Float -- ^ RGB Color

instance Show Color where
  show (Rgb r g b) = "rgb" ++ (show r) ++ (show g) ++ (show b)

-- | Create a new state dictionary for an alpha value           
newState :: Float -> PdfObject
newState a =  pdfDictionary [("Type",PdfName "ExtGState"),
                         ("CA",PdfFloat a),
                         ("ca",PdfFloat a)
                 ]
                     

                        
-- | Change the stroke color in a PDF document                    
strokeColor :: Color -> PdfCmd
strokeColor c  = case c of
                    Rgb r g b -> (PdfSC r g b,[])
                   
    
                            
-- | Change the fill color in a PDF document                    
fillColor :: Color -> PdfCmd
fillColor c  =  case c of
                    Rgb r g b -> (PdfSF r g b,[])
                   
                              
-- | Change the alpha setting for transparency in the document                  
setAlpha :: Float -> PdfCmd
setAlpha a  =  (PdfAlpha dictName,[(PdfState,dictName,PdfUnknownPointer dictName),
                (PdfAnyObject,dictName,newState a)]) 
                where
                    dictName = printf "alpha%f" a
                            

       
-- | Reset alpha value to opaque for stroke and fill colors                       
resetAlpha :: PdfCmd
resetAlpha = (PdfResetAlpha,[])
                            
-- | Set color space to RGB. Must always be used before starting to use any color.            
rgbSpace :: PdfCmd
rgbSpace  = (PdfRgbSpace,[])