getPointsInRandomTriangle

src/Lib.hs

@@ -2,6 +2,8 @@
 
 module Lib
 ( getRandomPixel
+, getPointsInTriangle
+, getPointsInRandomTriangle
 ) where
 
 
@@ -9,6 +11,8 @@ import Graphics.Image
 import qualified System.Random
 
 type Image_ = Image RPU RGB Double
+type Point = (Int, Int)
+type Triangle = (Point, Point, Point)
 
 getRandomPixel :: Image_ -> IO (Int, Int)
 getRandomPixel image = do
@@ -20,8 +24,27 @@ getRandomPixel image = do
         getCoord :: Int -> IO Int
         getCoord = System.Random.getStdRandom . System.Random.randomR . (1,)
 
--- makeGradGrayImage :: Image_
--- makeGradGrayImage = makeImageR RPU (200, 200) (\(i, j) -> PixelRGB $ fromIntegral (i*j)) / (200*200)
+getPointsInTriangle :: Image_ -> Triangle -> [Point]
+getPointsInTriangle image triangle
+    = filter (isPointInTriangle triangle)
+    $ (,) <$> [0..(rows image)] <*> [0..(cols image)]
 
--- displayGradGrayImage :: IO ()
--- displayGradGrayImage = displayImage makeGradGrayImage
+getPointsInRandomTriangle :: Image_ -> IO [Point]
+getPointsInRandomTriangle image = do
+    a <- getRandomPixel image
+    b <- getRandomPixel image
+    c <- getRandomPixel image
+    return $ getPointsInTriangle image (a, b, c)        
+
+isPointInTriangle :: Triangle -> Point -> Bool
+isPointInTriangle (v1, v2, v3) pt = not (has_neg && has_pos)
+    where
+        d1 = sign pt v1 v2
+        d2 = sign pt v2 v3
+        d3 = sign pt v3 v1
+
+        has_neg = (d1 < 0) || (d2 < 0) || (d3 < 0)
+        has_pos = (d1 > 0) || (d2 > 0) || (d3 > 0)
+
+        sign :: Point -> Point -> Point -> Int
+        sign p1 p2 p3 = (fst p1 - fst p3) * (snd p2 - snd p3) - (fst p2 - fst p3) * (snd p1 - snd p3)