Why would an image (the Mandelbrot) be skewed and wrap around?
- by Sean D
So I just wrote a little snippet to generate the Mandelbrot fractal and imagine my surprise when it came out all ugly and skewed (as you can see at the bottom). I'd appreciate a point in the direction of why this would even happen. It's a learning experience and I'm not looking for anyone to do it for me, but I'm kinda at a dead end debugging it. The offending generation code is:
module Mandelbrot where
import Complex
import Image
main = writeFile "mb.ppm" $ imageMB 1000
mandelbrotPixel x y = mb (x:+y) (0:+0) 0
mb c x iter
| magnitude x > 2 = iter
| iter >= 255 = 255
| otherwise = mb c (c+q^2) (iter+1)
where
q = x --Mandelbrot
--q = (abs.realPart $ x) :+ (abs.imagPart $ x) --Burning Ship
argandPlane x0 x1 y0 y1 width height =
[(x,y)| y<-[y1,(y1-dy)..y0], --traverse from
x<-[x0,(x0+dx)..x1]] --top-left to bottom-right
where
dx = (x1 - x0)/width
dy = (y1 - y0)/height
drawPicture :: (a->b->c)->(c->Colour)->[(a,b)]->Image
drawPicture function colourFunction plane =
map (colourFunction.uncurry function) plane
imageMB s = createPPM s s $
drawPicture mandelbrotPixel (\x->[x,x,x]) $
argandPlane (-1.8) (-1.7) (0.02) 0.055 s' s'
where s' = fromIntegral s
And the image code (which I'm fairly confident in) is:
module Image where
type Colour = [Int]
type Image = [Colour]
createPPM :: Int -> Int -> Image -> String
createPPM w h i =
concat ["P3 ", show w, " ", show h, " 255\n",
unlines.map (unwords.map show) $ i]
