-- | Basic definitions for stencil handling. module Data.Array.Repa.Stencil.Base ( Boundary (..) , Stencil (..) , makeStencil, makeStencil2) where import Data.Array.Repa.Index -- | How to handle the case when the stencil lies partly outside the array. data Boundary a -- | Treat points outside as having a constant value. = BoundConst a -- | Clamp points outside to the same value as the edge pixel. | BoundClamp deriving (Show) -- | Represents a convolution stencil that we can apply to array. -- Only statically known stencils are supported right now. data Stencil sh a -- | Static stencils are used when the coefficients are fixed, -- and known at compile time. = StencilStatic { stencilExtent :: !sh , stencilZero :: !a , stencilAcc :: !(sh -> a -> a -> a) } -- | Make a stencil from a function yielding coefficients at each index. makeStencil :: Num a => sh -- ^ Extent of stencil. -> (sh -> Maybe a) -- ^ Get the coefficient at this index. -> Stencil sh a {-# INLINE makeStencil #-} makeStencil ex getCoeff = StencilStatic ex 0 $ \ix val acc -> case getCoeff ix of Nothing -> acc Just coeff -> acc + val * coeff -- | Wrapper for `makeStencil` that requires a DIM2 stencil. makeStencil2 :: Num a => Int -> Int -- ^ extent of stencil -> (DIM2 -> Maybe a) -- ^ Get the coefficient at this index. -> Stencil DIM2 a {-# INLINE makeStencil2 #-} makeStencil2 height width getCoeff = makeStencil (Z :. height :. width) getCoeff