gistfile1.hs

-- | A scan-conversion algorithm for drawing lines on integral coordinate
-- systems. Returns the list of coordinates that should be filled to draw
-- the line from point to point.
line ::  (Integral a) => V2 a -> V2 a -> [V2 a]
line p p' = fmap near [0..end] where
  end    = case abs (p - p') of V2 dx dy -> max dx dy
  near i = round <$> lerp (i % end)
                          (fmap fromIntegral p')
                          (fmap fromIntegral p)


-- From Linear.Vector
-- | Linearly interpolate between two vectors.
lerp :: Num a => a -> f a -> f a -> f a
lerp alpha u v = alpha *^ u ^+^ (1 - alpha) *^ v

gistfile2.txt

> printLine $ line (V2 0 0) (V2 13 25)
 ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼ ◻
 ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◻ ◼

gistfile3.md

Computer Graphics – Practices and Principles 2ed