Bresenham样线算法

Question

我实现了一种算法，给出了应该绘制的点的列表，以便在两点之间得到一条线。请注意:它只在原点(0,0)位于左上角的坐标系中工作。

我想了解一下我的Haskell代码，它能在所使用的语言结构方面得到改进吗？它能更易读，更直接吗？

module DrawLine where

data Point = Point Float Float deriving (Show)

getRange :: Int -> Int -> [Int]
getRange a b
    | a <= b = [a..b]
    | otherwise = [b..a]
{-|
 - Get the slope of a line described by the two points received as arguments


-}
getSlope :: Point -> Point -> Float
getSlope (Point x1 y1) (Point x2 y2) = (y2-y1)/(x2-x1)

{-|
 - Get a list of points where pixels should be filled to draw a line
 - (Inspired from Bresenham's line algorithm)
 - Takes two Point arguments representing the end points of the line, the points
 - will be located on a line between these two points
 -}
getLinePoints :: Point -> Point -> [Point]
getLinePoints f@(Point fx fy) l@(Point lx ly)
    -- vertical line
    | fx == lx = [(Point fx (fromIntegral y)) | y <- getRange (round fy) (round ly)]
    | otherwise =
        -- generate points by mapping on the "longer side" of the line
        if m > 1.0 || m < -1.0 then
            -- the rise if higher than the run
            map (\y ->
                    (Point
                        ((1/m) * ((fromIntegral y) - fy) + fx)
                        (fromIntegral y)
                    )
                )
                (getRange (round fy) (round ly))
        else
            map (\x ->
                    (Point
                        (fromIntegral x)
                        (m * ((fromIntegral x) - fx) + fy)
                    )
                )
                (getRange (round fx) (round lx))
        where
            m = getSlope f l 

Answer 1

思想。

定义Line类型并将getLinePoints重命名为mkLine。一个点的列表可能代表任何东西，但Line [Points]却暗示着行内的Points。在可能的情况下，让类型系统为您工作。当然，你可以变得可爱，拥有Line (m -> x -> b -> [Points])或List Point Point。

您可以为Point和行类型定义Eq和Ord实例。

如果getSlope被传递给一条垂直线，该怎么办？它应该使用Maybe吗？

我会把非垂直线支持移动到它自己的功能中。也许还添加了一个水平线函数。

为什么对垂直行使用列表理解，而对其他类型的行使用map？这一切都可以通过理解来完成。