{-# LANGUAGE TemplateHaskell #-}
-- | Graphics algorithms and utils for rendering things in 2D space
--------------------------------------------------------------------------------
module Xanthous.Util.Graphics
( circle
, filledCircle
, line
, straightLine
, delaunay
-- * Debugging and testing tools
, renderBooleanGraphics
, showBooleanGraphics
) where
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import Xanthous.Prelude
--------------------------------------------------------------------------------
-- https://github.com/noinia/hgeometry/issues/28
-- import qualified Algorithms.Geometry.DelaunayTriangulation.DivideAndConquer
-- as Geometry
import qualified Algorithms.Geometry.DelaunayTriangulation.Naive
as Geometry
import qualified Algorithms.Geometry.DelaunayTriangulation.Types as Geometry
import Control.Monad.State (execState, State)
import qualified Data.Geometry.Point as Geometry
import Data.Ext ((:+)(..))
import Data.List (unfoldr)
import Data.List.NonEmpty (NonEmpty((:|)))
import qualified Data.List.NonEmpty as NE
import Data.Ix (Ix)
import Linear.V2
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-- | Generate a circle centered at the given point and with the given radius
-- using the <midpoint circle algorithm
-- https://en.wikipedia.org/wiki/Midpoint_circle_algorithm>.
--
-- Code taken from <https://rosettacode.org/wiki/Bitmap/Midpoint_circle_algorithm#Haskell>
circle :: (Num i, Ord i)
=> (i, i) -- ^ center
-> i -- ^ radius
-> [(i, i)]
circle (x₀, y₀) radius
-- Four initial points, plus the generated points
= (x₀, y₀ + radius) : (x₀, y₀ - radius) : (x₀ + radius, y₀) : (x₀ - radius, y₀) : points
where
-- Creates the (x, y) octet offsets, then maps them to absolute points in all octets.
points = concatMap generatePoints $ unfoldr step initialValues
generatePoints (x, y)
= [ (x₀ `xop` x', y₀ `yop` y')
| (x', y') <- [(x, y), (y, x)]
, xop <- [(+), (-)]
, yop <- [(+), (-)]
]
initialValues = (1 - radius, 1, (-2) * radius, 0, radius)
step (f, ddf_x, ddf_y, x, y)
| x >= y = Nothing
| otherwise = Just ((x', y'), (f', ddf_x', ddf_y', x', y'))
where
(f', ddf_y', y') | f >= 0 = (f + ddf_y' + ddf_x', ddf_y + 2, y - 1)
| otherwise = (f + ddf_x, ddf_y, y)
ddf_x' = ddf_x + 2
x' = x + 1
data FillState i
= FillState
{ _inCircle :: Bool
, _result :: NonEmpty (i, i)
}
makeLenses ''FillState
runFillState :: NonEmpty (i, i) -> State (FillState i) a -> [(i, i)]
runFillState circumference s
= toList
. view result
. execState s
$ FillState False circumference
-- | Generate a *filled* circle centered at the given point and with the given
-- radius by filling a circle generated with 'circle'
filledCircle :: (Num i, Integral i, Ix i)
=> (i, i) -- ^ center
-> i -- ^ radius
-> [(i, i)]
filledCircle origin radius =
case NE.nonEmpty (circle origin radius) of
Nothing -> []
Just circumference -> runFillState circumference $
-- the first and last lines of all circles are solid, so the whole "in the
-- circle, out of the circle" thing doesn't work... but that's fine since
-- we don't need to fill them. So just skip them
for_ [succ minX..pred maxX] $ \x ->
for_ [minY..maxY] $ \y -> do
let pt = (x, y)
next = (x, succ y)
whenM (use inCircle) $ result %= NE.cons pt
when (pt `elem` circumference && next `notElem` circumference)
$ inCircle %= not
where
((minX, minY), (maxX, maxY)) = minmaxes circumference
-- | Draw a line between two points using Bresenham's line drawing algorithm
--
-- Code taken from <https://wiki.haskell.org/Bresenham%27s_line_drawing_algorithm>
line :: (Num i, Ord i) => (i, i) -> (i, i) -> [(i, i)]
line pa@(xa, ya) pb@(xb, yb)
= (if maySwitch pa < maySwitch pb then id else reverse) points
where
points = map maySwitch . unfoldr go $ (x₁, y₁, 0)
steep = abs (yb - ya) > abs (xb - xa)
maySwitch = if steep then swap else id
[(x₁, y₁), (x₂, y₂)] = sort [maySwitch pa, maySwitch pb]
δx = x₂ - x₁
δy = abs (y₂ - y₁)
ystep = if y₁ < y₂ then 1 else -1
go (xTemp, yTemp, err)
| xTemp > x₂ = Nothing
| otherwise = Just ((xTemp, yTemp), (xTemp + 1, newY, newError))
where
tempError = err + δy
(newY, newError) = if (2 * tempError) >= δx
then (yTemp + ystep, tempError - δx)
else (yTemp, tempError)
straightLine :: (Num i, Ord i) => (i, i) -> (i, i) -> [(i, i)]
straightLine pa@(xa, _) pb@(_, yb) = line pa midpoint ++ line midpoint pb
where midpoint = (xa, yb)
delaunay
:: (Ord n, Fractional n)
=> NonEmpty (V2 n, p)
-> [((V2 n, p), (V2 n, p))]
delaunay
= map (over both fromPoint)
. Geometry.triangulationEdges
. Geometry.delaunayTriangulation
. map toPoint
where
toPoint (V2 px py, pid) = Geometry.Point2 px py :+ pid
fromPoint (Geometry.Point2 px py :+ pid) = (V2 px py, pid)
--------------------------------------------------------------------------------
renderBooleanGraphics :: forall i. (Num i, Ord i, Enum i) => [(i, i)] -> String
renderBooleanGraphics [] = ""
renderBooleanGraphics (pt : pts') = intercalate "\n" rows
where
rows = row <$> [minX..maxX]
row x = [minY..maxY] <&> \y -> if (x, y) `member` ptSet then 'X' else ' '
((minX, minY), (maxX, maxY)) = minmaxes pts
pts = pt :| pts'
ptSet :: Set (i, i)
ptSet = setFromList $ toList pts
showBooleanGraphics :: forall i. (Num i, Ord i, Enum i) => [(i, i)] -> IO ()
showBooleanGraphics = putStrLn . pack . renderBooleanGraphics
minmaxes :: forall i. (Ord i) => NonEmpty (i, i) -> ((i, i), (i, i))
minmaxes xs =
( ( minimum1Of (traverse1 . _1) xs
, minimum1Of (traverse1 . _2) xs
)
, ( maximum1Of (traverse1 . _1) xs
, maximum1Of (traverse1 . _2) xs
)
)
