Re: [OctDev] imrotate

[Todd N. <to...@gm...>]

On Tue, 15 Feb 2005 23:58:04 -0500, Paul Kienzle <pki...@us...> wrote:
> I replaced the old version of imrotate with what you sent.
> 
> I would appreciate a few simple test cases which do not
> rely on a human visual system to determine if the result
> is correct.
> 
> I tried the following:
> 
>         X = rand(30);
>         Y = imrotate(imrotate(X,30,'bicubic'),-30,'bicubic');
>         norm(X(17+[1:5],17+[1:5])-Y(30+[1:5],30+[1:5]))
>         ans = 0.46103
> 
> Using a smoother function worked better:
> 
>         X = peaks(30);
>         Y = imrotate(imrotate(X,30,'bicubic'),-30,'bicubic');
>         norm(X(17+[1:5],17+[1:5])-Y(30+[1:5],30+[1:5]))
>         ans = 0.0036647
> 
> Anyone have any better suggestions?
> 

I was looking for a few good test cases and came across using this as
a test case:

imrotate(eye(20),45)

The problem is displayed here (in a smaller case to fit in an email well):

octave:18> imrotate(eye(13),45)
ans =

  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  1  0  0  1  0  0  0  1  0  0  1  0  0  0  1  0  0  1
  1  0  0  1  0  0  0  1  0  0  1  0  0  0  1  0  0  1
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0


Todd