# arirahikkala/straylight-divergence

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 module Mapgen.FindRectangles where import Rect import Mapgen.Rect import BasicTypes import Data.Set (Set) import qualified Data.Set as Set import Data.List (minimumBy) import Data.AdditiveGroup ((^-^)) import Data.VectorSpace (magnitudeSq) import Data.Ord (comparing) import Control.Arrow ((&&&)) import Data.PSQueue (PSQ) import qualified Data.PSQueue as PSQ -- Whitespace rectangle finder. Based on TM Breuel, Two Geometric Algorithms For -- Layout Analysis, Workshop on Document Analysis Systems 2002, pp. 188-199. Or -- if you're a normal person who just clicks on hyperlinks rather than track -- references down by paper and all that, -- http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.17.5758&rep=rep1&type=pdf findRectangles :: (BoundsRect) -> [BoundsRect] -> [BoundsRect] findRectangles boundary obstacles = go (PSQ.singleton boundary (poorness boundary obstacles)) obstacles where go q os = case PSQ.minView q of Nothing -> [] Just (r PSQ.:-> pri, newQ) -> if pri /= poorness r os then go (PSQ.insert r (poorness r os) newQ) os else let pivot = pick r . within r \$ os clear = noObstacles r os dirs = map (id &&& flip poorness os) \$ filter ((> 0) . boundsRectSize) \$ [clampNorth pivot r, clampSouth pivot r, clampWest pivot r, clampEast pivot r] in if clear then r : go newQ (r : os) else go (foldr (uncurry PSQ.insert) newQ dirs) os noObstacles r = all ((== 0) . boundsRectSize) . map (rectClamp r) -- proly could come up with better sampling strategies than just taking a -- couple of the first obstacles, but ehh -- (fwiw just taking the first one always would probably be perfectly good enough and quite possibly not any worse than this) pick r os = minimumBy (comparing (magnitudeSq . (approximateCenter r ^-^) . approximateCenter)) \$ take 3 os within r = filter ((>0) . boundsRectSize) . map (rectClamp r) -- the smaller the poorness, the better! poorness r os = Set.size (Set.fromList \$ concatMap (rectCoords . rectClamp r) os) - boundsRectSize r - (uncurryCoord min \$ uncurry (^-^) \$ r) uncurryCoord f (Coord x y) = f x y rectClamp (Coord xBigStart yBigStart, Coord xBigEnd yBigEnd) (Coord xSmallStart ySmallStart, Coord xSmallEnd ySmallEnd) = (Coord (max xBigStart xSmallStart) (max yBigStart ySmallStart), Coord (min xBigEnd xSmallEnd) (min yBigEnd ySmallEnd)) clampNorth (Coord xBigStart yBigStart, Coord xBigEnd yBigEnd) (Coord xSmallStart ySmallStart, Coord xSmallEnd ySmallEnd) = (Coord xSmallStart (min ySmallStart yBigStart), Coord xSmallEnd (min ySmallEnd yBigStart)) clampSouth (Coord xBigStart yBigStart, Coord xBigEnd yBigEnd) (Coord xSmallStart ySmallStart, Coord xSmallEnd ySmallEnd) = (Coord xSmallStart (max ySmallStart yBigEnd), Coord xSmallEnd (max ySmallEnd yBigEnd)) clampWest (Coord xBigStart yBigStart, Coord xBigEnd yBigEnd) (Coord xSmallStart ySmallStart, Coord xSmallEnd ySmallEnd) = (Coord (min xSmallStart xBigStart) ySmallStart, Coord (min xSmallEnd xBigStart) ySmallEnd) clampEast (Coord xBigStart yBigStart, Coord xBigEnd yBigEnd) (Coord xSmallStart ySmallStart, Coord xSmallEnd ySmallEnd) = (Coord (max xSmallStart xBigEnd) ySmallStart, Coord (max xSmallEnd xBigEnd) ySmallEnd)