module Graphics.Image.Processing.Convolution (
convolve, convolveRows, convolveCols, correlate
) where
import Prelude as P
import Graphics.Image.ColorSpace
import Graphics.Image.Interface as I
import Graphics.Image.Processing.Geometric
correlate :: I.Array arr cs e =>
Border (Pixel cs e) -> Image arr cs e -> Image arr cs e -> Image arr cs e
correlate !border !kernel !img =
I.traverse (compute img) (const sz) stencil
where
!kernelM = toManifest kernel
!(krnM, krnN) = dims kernelM
!krnM2 = krnM `div` 2
!krnN2 = krnN `div` 2
!sz = dims img
getPxB getPx !ix = handleBorderIndex border sz getPx ix
stencil getImgPx !(i, j) = integrate 0 0 0 where
!ikrnM = i krnM2
!jkrnN = j krnN2
integrate !ki !kj !acc
| kj == krnN = integrate (ki+1) 0 acc
| kj == 0 && ki == krnM = acc
| otherwise = let !krnPx = I.unsafeIndex kernelM (ki, kj)
!imgPx = getPxB getImgPx (ki + ikrnM, kj + jkrnN)
in integrate ki (kj + 1) (acc + krnPx * imgPx)
convolve :: Array arr cs e =>
Border (Pixel cs e)
-> Image arr cs e
-> Image arr cs e
-> Image arr cs e
convolve !out = correlate out . rotate180
convolveRows :: Array arr cs e =>
Border (Pixel cs e) -> [Pixel cs e] -> Image arr cs e -> Image arr cs e
convolveRows !out = convolve out . fromLists . (:[]) . reverse
convolveCols :: Array arr cs e =>
Border (Pixel cs e) -> [Pixel cs e] -> Image arr cs e -> Image arr cs e
convolveCols !out = convolve out . fromLists . P.map (:[]) . reverse