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import System.IO
import Data.Char
import Debug.Trace
w = 192 * 4
h = 108 * 4
type Color = (Int, Int, Int) -- red green blue
darkness = (0, 0, 50)
starlight = (250, 250, 180)
colormix :: Double -> Color -> Color -> Color
colormix amount c1 c2 = (round $ p*fromIntegral r1 + (1-p)*fromIntegral r2,
round $ p*fromIntegral g1 + (1-p)*fromIntegral g2,
round $ p*fromIntegral b1 + (1-p)*fromIntegral b2)
where (r1, g1, b1) = c1
(r2, g2, b2) = c2
p = max 0 $ min 1 amount
imgheader = "P3 " ++ (show w) ++ " " ++ (show h) ++ " 255\n"
cartProd xs ys = [(x,y) | y <- ys, x <- xs]
pixels = cartProd (take w [0,1..]) (take h [0,1..])
star_luminosity crit (x, y) = fromIntegral
(min 4 $
( ((x^2 + y^3 + (x+y+2)^3) `mod` (256)) `div` (256 `div` crit) )
) / 4
stardist :: (Int, Int) -> (Int, Int) -> Double
stardist p1 p2 = sqrt $ fromIntegral ( (x1-x2)^2 + (y1-y2)^2)
where (x1, y1) = p1
(x2, y2) = p2
roughness = 5
nearest_potential_star_centre :: (Int, Int) -> (Int, Int)
nearest_potential_star_centre (x, y) = ((x `div` roughness) * roughness + (roughness `div` 2),
(y `div` roughness) * roughness + (roughness `div` 2))
star_color crit (x, y) = colormix (lum * (stardist (x,y) nearest) / 2 ) darkness starlight
where nearest = nearest_potential_star_centre (x,y)
lum = star_luminosity crit nearest
pixel_to_ppm :: Color -> String
pixel_to_ppm (r,g,b) = show r ++ " " ++ show g ++ " " ++ show b ++ "\n"
image :: Int -> String
image crit = imgheader ++ (foldr (++) "" (map (pixel_to_ppm . star_color crit) pixels))
write_sky :: Int -> IO ()
write_sky crit = trace ("Rendering " ++ show crit)
writeFile ("skyimg/sky" ++ show crit ++ ".ppm") (image crit)
main = mapM write_sky [2, 20,30,40,50]
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