Complex.hs

{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE FlexibleContexts #-}
-- |
-- Module      : Graphics.Image.Processing.Complex
-- Copyright   : (c) Alexey Kuleshevich 2016
-- License     : BSD3
-- Maintainer  : Alexey Kuleshevich <lehins@yandex.ru>
-- Stability   : experimental
-- Portability : non-portable
--
module Graphics.Image.Processing.Complex (
  -- * Rectangular form
  (!+!), realPartI, imagPartI,
  -- * Polar form
  mkPolarI, cisI, polarI, magnitudeI, phaseI,
  -- * Conjugate
  conjugateI,
  -- ** Fourier Transform
  fft, ifft
  ) where

import Prelude hiding (map, zipWith)
import Graphics.Image.Interface
import Graphics.Image.ColorSpace.Complex
import Graphics.Image.Processing.Complex.Fourier


infix 6 !+!

-- | Construct a complex image from two images representing real and imaginary parts.
--
-- >>> frog <- readImageRGB VU "images/frog.jpg"
-- >>> frog !+! 0
-- <Image VectorUnboxed RGB (Complex Double): 200x320>
-- >>> frog !+! frog
-- <Image VectorUnboxed RGB (Complex Double): 200x320>
--
(!+!) :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e)) =>
         Image arr cs e -> Image arr cs e -> Image arr cs (Complex e)
(!+!) = zipWith (+:)
{-# INLINE (!+!) #-}

-- | Extracts the real part of a complex image.
realPartI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
             Image arr cs (Complex e) -> Image arr cs e
realPartI = map realPart
{-# INLINE realPartI #-}

-- | Extracts the imaginary part of a complex image.
imagPartI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
             Image arr cs (Complex e) -> Image arr cs e
imagPartI = map imagPart
{-# INLINE imagPartI #-}

-- | Form a complex image from polar components of magnitude and phase.
mkPolarI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
            Image arr cs e -> Image arr cs e -> Image arr cs (Complex e)
mkPolarI = zipWith mkPolar
{-# INLINE mkPolarI #-}

-- | @'cisI' t@ is a complex image with magnitude 1 and phase t (modulo @2*'pi'@).
cisI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
        Image arr cs e -> Image arr cs (Complex e)
cisI = map cis
{-# INLINE cisI #-}

-- | The function @'polar''@ takes a complex image and returns a (magnitude, phase)
-- pair of images in canonical form: the magnitude is nonnegative, and the phase
-- in the range @(-'pi', 'pi']@; if the magnitude is zero, then so is the phase.
polarI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
          Image arr cs (Complex e) -> (Image arr cs e, Image arr cs e)
polarI !zImg = (magnitudeI zImg, phaseI zImg)
{-# INLINE polarI #-}

-- | The nonnegative magnitude of a complex image.
magnitudeI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
              Image arr cs (Complex e) -> Image arr cs e
magnitudeI = map magnitude
{-# INLINE magnitudeI #-}

-- | The phase of a complex image, in the range @(-'pi', 'pi']@. If the
-- magnitude is zero, then so is the phase.
phaseI :: (Applicative (Pixel cs), Array arr cs e, Array arr cs (Complex e), RealFloat e) =>
          Image arr cs (Complex e) -> Image arr cs e
phaseI = map phase
{-# INLINE phaseI #-}

-- | The conjugate of a complex image.
conjugateI :: (Applicative (Pixel cs), Array arr cs (Complex e), RealFloat e) =>
              Image arr cs (Complex e) -> Image arr cs (Complex e)
conjugateI = map conjugate
{-# INLINE conjugateI #-}