Copyright | (c) Alexey Kuleshevich 2018 |
---|---|
License | BSD3 |
Maintainer | Alexey Kuleshevich <lehins@yandex.ru> |
Stability | experimental |
Portability | non-portable |
Safe Haskell | None |
Language | Haskell2010 |
- data Stencil ix e a
- data Value e
- mapStencil :: (Source r ix e, Manifest r ix e) => Stencil ix e a -> Array r ix e -> Array DW ix a
- makeStencil :: (Index ix, Default e) => Border e -> ix -> ix -> ((ix -> Value e) -> Value a) -> Stencil ix e a
- makeConvolutionStencil :: (Index ix, Num e) => Border e -> ix -> ix -> ((ix -> Value e -> Value e -> Value e) -> Value e -> Value e) -> Stencil ix e e
- makeConvolutionStencilFromKernel :: (Manifest r ix e, Num e) => Border e -> Array r ix e -> Stencil ix e e
Documentation
Stencil is abstract description of how to handle elements in the neighborhood of every array
cell in order to compute a value for the cells in the new array. Use makeStencil
and
makeConvolutionStencil
in order to create a stencil.
Functor (Stencil ix e) Source # | |
(Default e, Index ix) => Applicative (Stencil ix e) Source # | |
(Index ix, Default e, Floating a) => Floating (Stencil ix e a) Source # | |
(Index ix, Default e, Fractional a) => Fractional (Stencil ix e a) Source # | |
(Index ix, Default e, Num a) => Num (Stencil ix e a) Source # | |
(NFData e, Index ix) => NFData (Stencil ix e a) Source # | |
This is a simple wrapper for value of an array cell. It is used in order to improve safety of
Stencil
mapping. Using various class instances, such as Num
and Functor
for example, make
it possible to manipulate the value, without having direct access to it.
Functor Value Source # | |
Applicative Value Source # | |
Bounded e => Bounded (Value e) Source # | |
Eq e => Eq (Value e) Source # | |
Floating e => Floating (Value e) Source # | |
Fractional e => Fractional (Value e) Source # | |
Num e => Num (Value e) Source # | |
Ord e => Ord (Value e) Source # | |
Show e => Show (Value e) Source # | |
mapStencil :: (Source r ix e, Manifest r ix e) => Stencil ix e a -> Array r ix e -> Array DW ix a Source #
Map a constructed stencil over an array. Resulting array must be compute
d in order to be
useful.
:: (Index ix, Default e) | |
=> Border e | Border resolution technique |
-> ix | Size of the stencil |
-> ix | Center of the stencil |
-> ((ix -> Value e) -> Value a) | Stencil function that receives a "get" function as it's argument that can retrieve values of cells in the source array with respect to the center of the stencil. Stencil function must return a value that will be assigned to the cell in the result array. Offset supplied to the "get" function cannot go outside the boundaries of the stencil, otherwise an error will be raised during stencil creation. |
-> Stencil ix e a |
Construct a stencil from a function, which describes how to calculate the value at a point while having access to neighboring elements with a function that accepts idices relative to the center of stencil. Trying to index outside the stencil box will result in a runtime error upon stencil creation.
Example
Below is an example of creating a Stencil
, which, when mapped over a
2-dimensional array, will compute an average of all elements in a 3x3 square
for each element in that array. Note: Make sure to add INLINE
pragma,
otherwise performance will be terrible.
average3x3Stencil :: (Default a, Fractional a) => Border a -> Stencil Ix2 a a average3x3Stencil b = makeStencil b (3 :. 3) (1 :. 1) $ \ get -> ( get (-1 :. -1) + get (-1 :. 0) + get (-1 :. 1) + get ( 0 :. -1) + get ( 0 :. 0) + get ( 0 :. 1) + get ( 1 :. -1) + get ( 1 :. 0) + get ( 1 :. 1) ) / 9 {-# INLINE average3x3Stencil #-}
makeConvolutionStencil :: (Index ix, Num e) => Border e -> ix -> ix -> ((ix -> Value e -> Value e -> Value e) -> Value e -> Value e) -> Stencil ix e e Source #
Create a convolution stencil by specifying border resolution technique and an accumulator function.
Examples
Here is how to create a 2D horizontal Sobel Stencil:
sobelX :: Num e => Border e -> Stencil Ix2 e e sobelX b = makeConvolutionStencil b (3 :. 3) (1 :. 1) $ \f -> f (-1 :. -1) 1 . f (-1 :. 1) (-1) . f ( 0 :. -1) 2 . f ( 0 :. 1) (-2) . f ( 1 :. -1) 1 . f ( 1 :. 1) (-1) {-# INLINE sobelX #-}
makeConvolutionStencilFromKernel :: (Manifest r ix e, Num e) => Border e -> Array r ix e -> Stencil ix e e Source #
Make a stencil out of a Kernel Array. This Stencil
will be slower than if
makeConvolutionStencil
is used, but sometimes we just really don't know the
kernel at compile time.