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Diffstat (limited to 'src/Xanthous/Util/Graphics.hs')
-rw-r--r-- | src/Xanthous/Util/Graphics.hs | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/src/Xanthous/Util/Graphics.hs b/src/Xanthous/Util/Graphics.hs new file mode 100644 index 000000000000..5a174d4f415b --- /dev/null +++ b/src/Xanthous/Util/Graphics.hs @@ -0,0 +1,64 @@ +-- | 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 <midpoint circle algorithm +-- https://en.wikipedia.org/wiki/Midpoint_circle_algorithm>. +-- +-- Code taken from <https://rosettacode.org/wiki/Bitmap/Midpoint_circle_algorithm#Haskell> +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 <https://wiki.haskell.org/Bresenham%27s_line_drawing_algorithm> +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) |