-- |
-- Module : Codec.Picture.Extra
-- Copyright : © 2016 Mark Karpov
-- License : BSD 3 clause
--
-- Maintainer : Mark Karpov <markkarpov@openmailbox.org>
-- Stability : experimental
-- Portability : portable
--
-- Utilities for image transformation with JuicyPixels.
{-# LANGUAGE RecordWildCards #-}
module Codec.Picture.Extra
( -- * Scaling
scaleBilinear
-- * Cropping
, crop
-- * Rotation
, flipHorizontally
, flipVertically
, rotateLeft90
, rotateRight90 )
where
import Codec.Picture
import Control.Monad.ST
import qualified Codec.Picture.Types as M
-- | Scale image using bi-linear interpolation. This is specialized to
-- 'PixelRGB8' only for speed (polymorphic version is easily written, but
-- it's more than twice as slow).
scaleBilinear
:: Int -- ^ Desired width
-> Int -- ^ Desired height
-> Image PixelRGB8 -- ^ Original image
-> Image PixelRGB8 -- ^ Scaled image
scaleBilinear width height img@Image {..} = runST $ do
mimg <- M.newMutableImage width height
let sx, sy :: Float
sx = fromIntegral imageWidth / fromIntegral width
sy = fromIntegral imageHeight / fromIntegral height
go x' y'
| x' >= width = go 0 (y' + 1)
| y' >= height = M.unsafeFreezeImage mimg
| otherwise = do
let xf = fromIntegral x' * sx
yf = fromIntegral y' * sy
x, y :: Int
x = floor xf
y = floor yf
δx = xf - fromIntegral x
δy = yf - fromIntegral y
pixelAt' i j =
if i >= imageWidth || j >= imageHeight
then PixelRGB8 0 0 0
else pixelAt img i j
writePixel mimg x' y' $
mulp (pixelAt' x y) ((1 - δx) * (1 - δy)) `addp`
mulp (pixelAt' (x + 1) y) (δx * (1 - δy)) `addp`
mulp (pixelAt' x (y + 1)) ((1 - δx) * δy) `addp`
mulp (pixelAt' (x + 1) (y + 1)) (δx * δy)
go (x' + 1) y'
go 0 0
mulp :: PixelRGB8 -> Float -> PixelRGB8
mulp pixel x = colorMap (floor . (* x) . fromIntegral) pixel
{-# INLINE mulp #-}
addp :: PixelRGB8 -> PixelRGB8 -> PixelRGB8
addp = mixWith (const f)
where
f x y = fromIntegral $
(0xff :: Pixel8) `min` (fromIntegral x + fromIntegral y)
{-# INLINE addp #-}
-- | Crop given image. If supplied coordinates are greater than size of
-- original image, image boundaries are used instead.
crop :: Pixel a
=> Int -- ^ Index (X axis) of first pixel to include
-> Int -- ^ Index (Y axis) of first pixel to include
-> Int -- ^ Width of resulting image
-> Int -- ^ Height of resulting image
-> Image a -- ^ Original image
-> Image a -- ^ Cropped image
crop x' y' w' h' img@Image {..} =
generateImage gen w h
where
gen i j = pixelAt img (x + i) (y + j)
x = min (imageWidth - 1) x'
y = min (imageHeight - 1) y'
w = min (imageWidth - x) w'
h = min (imageWidth - y) h'
-- | Flip image horizontally.
flipHorizontally :: Pixel a => Image a -> Image a
flipHorizontally img@Image {..} =
generateImage gen imageWidth imageHeight
where
gen x = pixelAt img (imageWidth - 1 - x)
-- | Flip image vertically.
flipVertically :: Pixel a => Image a -> Image a
flipVertically img@Image {..} =
generateImage gen imageWidth imageHeight
where
gen x y = pixelAt img x (imageHeight - 1 - y)
-- | Rotate image to the left by 90°.
rotateLeft90 :: Pixel a => Image a -> Image a
rotateLeft90 img@Image {..} =
generateImage gen imageHeight imageWidth
where
gen x y = pixelAt img y x
-- | Rotate image to the right by 90°.
rotateRight90 :: Pixel a => Image a -> Image a
rotateRight90 img@Image {..} =
generateImage gen imageHeight imageWidth
where
gen x y = pixelAt img y (imageHeight - 1 - x)