Format.hs

{-# LANGUAGE RecordWildCards #-}

-- | This module contains the pixel formats supprted my babl
module BABL.Format
  ( FFI.PixelFormat(..)
  , FFI.ComponentModel(..)
  , FFI.ComponentFormat(..)
  , FFI.BablFormatPtr
  , babl_format
  , babl_get_bpp
  , babl_format_by_str
  , babl_components_per_pixel
  ) where

import qualified BABL.FFI.Format as FFI

import Foreign.C.String (withCString)
import Foreign.C.Types (CInt(..))

babl_components_per_pixel :: FFI.PixelFormat -> Int
babl_components_per_pixel FFI.PixelFormat{..} =
  case pfComponents of
    FFI.RGB        -> 3
    FFI.RGBA       -> 4
    FFI.RaGaBaA    -> 4
    FFI.R'G'B'     -> 3
    FFI.R'G'B'A    -> 4
    FFI.R'aG'aB'aA -> 4
    FFI.Y          -> 1
    FFI.YA         -> 2
    FFI.YaA        -> 2
    FFI.Y'         -> 1
    FFI.Y'A        -> 2
    FFI.Y'aA       -> 2
    FFI.Y'CbCr     -> 3
    FFI.Y'CbCrA    -> 4
    FFI.HSVA       -> 4
    FFI.HSV        -> 3
    FFI.CMYK       -> 4
    FFI.CMY        -> 3
    FFI.CIELab     -> 3
    FFI.CIELabAlpha   -> 4
    FFI.CIELCHab      -> 3
    FFI.CIELCHabAlpha -> 4
    FFI.HSLA          -> 4
    FFI.HSL           -> 3
    FFI.Y'CbCr709     -> 3
    FFI.Y'CbCrA709    -> 4
    FFI.Cairo         -> case pfType of
      FFI.A8     -> 1
      FFI.RGB24  -> 4
      FFI.ARGB32 -> 4
      _          -> error "wrong type"

-- | Create a 'BablFormatPtr' to pass around to other functions.
babl_format
  :: FFI.PixelFormat        -- ^ Format to be used
  -> IO FFI.BablFormatPtr -- ^ Pointer to specified format
babl_format (FFI.PixelFormat FFI.Cairo pfType) =
  case pfType of
    FFI.A8     -> babl_format_by_str "cairo-A8"
    FFI.RGB24  -> babl_format_by_str "cairo-RGB24"
    FFI.ARGB32 -> babl_format_by_str "cairo-ARGB32"
    _          -> error "not a cairo format"
babl_format FFI.PixelFormat{..} =
  babl_format_by_str (show pfComponents ++ " " ++ show pfType)

-- | Build 'BablFormatPtr' by input String
babl_format_by_str
  :: String -- ^ Input string
  -> IO FFI.BablFormatPtr
babl_format_by_str s =
  return . FFI.BablFormatPtr =<< withCString s FFI.c_babl_format

-- | Peek the number of bytes per pixel from a format.
babl_get_bpp
  :: FFI.PixelFormat -- ^ Format to peek from
  -> IO Int
babl_get_bpp form = do
  (FFI.BablFormatPtr ptr) <- babl_format form
  (CInt res) <- FFI.c_babl_get_bpp ptr
  return $ fromIntegral res