Rotation Matrix PBMfile Haskell

Question

Possible Duplicate:
Rotate Image .pbm Haskell

i need help about a rotation matrix in haskell

i have 2 data type:

data RGBdata= RGB Int Int Int
data PBMfile= PBM Int Int [[RGBdata]]

and my function receive:

spin :: PBMfile -> PBMfile
spin (PBM x y l) = (PBM x y ((transpose . reverse) l))

where 'x' and 'y' is the number of colums and rows respectively (maybe can help to do the function).

for example:

(PBM 2 2 [[(RGB 0 255 255),(RGB 255 0 0)],[(RGB 255 255 255),(RGB 255 0 0)]])

I try rotate 90° to the left using combinations with reverse and transpose, but the image result is wrong.

i try

spin :: PBMfile -> PBMfile
spin (PBM x y l) = (PBM x y ((reverse . transpose) l))

and

spin :: PBMfile -> PBMfile
spin (PBM x y l) = (PBM x y ((transpose . reverse) l))

and

spin :: PBMfile -> PBMfile
spin (PBM x y l) = (PBM x y (((map reverse) . transpose) l))

to rotate the matrix but does not work.

the result is something like

"the image result is wrong"... but wrong in what way? Try phrasing your question in the form "I did X, expecting Y, but Z happened instead.". — Daniel Wagner, May 02 '12 at 06:42
Not only for us to understand, but also for you to test your functions. What is the result of applying kunwoo32's solution to your own example? — Hans Lub, May 02 '12 at 09:07

score 2 · Answer 1 · edited May 02 '12 at 07:59

2

The transpose operation should happen before the reverse operation. Try

spin (PBM x y l) = (PBM y x ((reverse . transpose) l))

Also the dimensions of the rotated images are switched.

edited May 02 '12 at 07:59

dave4420

answered May 02 '12 at 06:23

kunwoo32

I try, and does not work .. I get the image has a diagonal line that divide it. thanks – user495943 May 02 '12 at 06:31
In your example in your question, your matrix seems to be rotating clockwise. Is that what you want? – kunwoo32 May 02 '12 at 06:53
yes, to rotate the image – user495943 May 02 '12 at 07:38

score 1 · Answer 2 · answered May 02 '12 at 10:32

1

You need to also consider (map reverse), not just transpose and reverse. I think ((map reverse) . transpose) does what you want.

answered May 02 '12 at 10:32

Chris Kuklewicz

does not work men, i try and and is really close but is reversed – user495943 May 02 '12 at 11:02

2 Answers2