Base.hs

{-# LANGUAGE BangPatterns          #-}
{-# LANGUAGE ConstraintKinds       #-}
{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies          #-}
-- |
-- Module      : Graphics.Image.IO.Base
-- Copyright   : (c) Alexey Kuleshevich 2016
-- License     : BSD3
-- Maintainer  : Alexey Kuleshevich <lehins@yandex.ru>
-- Stability   : experimental
-- Portability : non-portable
--
module Graphics.Image.IO.Base (
  ImageFormat(..), Readable(..), Writable(..), Convertible(..), Seq(..), ComplexWritable
  ) where

import qualified Data.ByteString                     as B (ByteString)
import qualified Data.ByteString.Lazy                as BL (ByteString)
import           Graphics.Image.ColorSpace
import           Graphics.Image.Interface            as I
import           Graphics.Image.Processing.Complex   (imagPartI, realPartI)
import           Graphics.Image.Processing.Geometric (leftToRight)

-- | Used during converting pixels between libraries.
class Convertible cs e where
  convert :: (ToYA cs' e', ToRGBA cs' e', Array arr cs' e', Array arr cs e) =>
    Image arr cs' e' -> Image arr cs e


instance Convertible Y Double where
  convert = toImageY

instance Convertible YA Double where
  convert = toImageYA

instance Convertible RGB Double where
  convert = toImageRGB

instance Convertible RGBA Double where
  convert = toImageRGBA


-- | Special wrapper for formats that support encoding/decoding sequence of images.
newtype Seq f = Seq f

-- | Image file format. Helps in guessing image format using a file extension,
-- as well as supplying format specific options during saving an image.
class ImageFormat format where
  -- | Options that can be used during writing an image in this format.
  data SaveOption format

  -- | Default file extension for this image format.
  ext :: format -> String

  -- | Known file extensions for this image format, if more than one is commonly
  -- used, eg. ".jpeg", ".jpg".
  exts :: format -> [String]
  exts f = [ext f]

  -- | Checks if a file extension
  -- corresponds to the format, eg. @isFormat ".png" PNG == True@
  isFormat :: String -> format -> Bool
  isFormat e f = e `elem` exts f


-- | Image formats that can be read from file.
class ImageFormat format => Readable img format where

  -- | Decode an image from `BL.ByteString`.
  decode :: format -> B.ByteString -> Either String img


-- | Image formats that can be written to file.
class ImageFormat format => Writable img format where

  -- | Encode an image into `BL.ByteString`.
  encode :: format -> [SaveOption format] -> img -> BL.ByteString

-- | Constraint type synonym for encoding a Complex image.
type ComplexWritable format arr cs e = ( Array arr cs e, Array arr cs (Complex e)
                                       , RealFloat e, Applicative (Pixel cs)
                                       , Writable (Image arr cs e) format )


-- | Writing Complex images: places real part on the left side of imaginary part.
instance ComplexWritable format arr cs e => Writable (Image arr cs (Complex e)) format where
  encode format opts !imgC =
    encode format opts (leftToRight (realPartI imgC) (imagPartI imgC))