# Difference between revisions of "Bresenham's line drawing algorithm"

From HaskellWiki

m |
|||

(One intermediate revision by one other user not shown) | |||

Line 28: | Line 28: | ||

The core logic is in the "go" function which is passed to unfoldr. |
The core logic is in the "go" function which is passed to unfoldr. |
||

+ | |||

+ | And here is an implementation of generalized Bresenham's line drawing algorithm, in terms of balanced words: https://github.com/LambdaHack/LambdaHack/blob/2f031f8a09d07d46b8e0dfeff1d9653d31ea19cc/Game/LambdaHack/Common/Point.hs#L112 |
||

+ | |||

+ | [[Category:Code]] |

## Latest revision as of 23:01, 11 July 2021

```
import List (sort,unfoldr)
type Point = (Integer,Integer)
line :: Point -> Point -> [Point]
line pa@(xa,ya) pb@(xb,yb) = map maySwitch . unfoldr go $ (x1,y1,0)
where
steep = abs (yb - ya) > abs (xb - xa)
maySwitch = if steep then (\(x,y) -> (y,x)) else id
[(x1,y1),(x2,y2)] = sort [maySwitch pa, maySwitch pb]
deltax = x2 - x1
deltay = abs (y2 - y1)
ystep = if y1 < y2 then 1 else -1
go (xTemp, yTemp, error)
| xTemp > x2 = Nothing
| otherwise = Just ((xTemp, yTemp), (xTemp + 1, newY, newError))
where
tempError = error + deltay
(newY, newError) = if (2*tempError) >= deltax
then (yTemp+ystep,tempError-deltax)
else (yTemp,tempError)
```

Thanks to Cheddai Fouche for the above implementation.

The core logic is in the "go" function which is passed to unfoldr.

And here is an implementation of generalized Bresenham's line drawing algorithm, in terms of balanced words: https://github.com/LambdaHack/LambdaHack/blob/2f031f8a09d07d46b8e0dfeff1d9653d31ea19cc/Game/LambdaHack/Common/Point.hs#L112