-- | Graphics algorithms and utils for rendering things in 2D space -------------------------------------------------------------------------------- module Xanthous.Util.Graphics where -------------------------------------------------------------------------------- import Xanthous.Prelude import Data.List (unfoldr) -------------------------------------------------------------------------------- -- | Generate a circle centered at the given point and with the given radius -- using the . -- -- Code taken from 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 -- | Draw a line between two points using Bresenham's line drawing algorithm -- -- Code taken from 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)