Hi Chenitz,
    It sounds like you may be using fftshift on one of your transformations 
and  not the other - I'd just check your code to see if this might be 
happening before worrying about anything more complicated.

Best of Luck - Mike

"chenitz" <chenitz@yahoo.com> wrote in message 
news:5f35af74.0501280022.b61c37f@posting.google.com...
> Hi,
>
> I created an image in Matlab in the following way: I created 2 vectors
> that represent the image coordinates, and gave a value to each
> combination of the vectors. For example: a=[-0.4:0.02:0.4], b=a,
> image(y,x) is the value of a(y), b(x). Then I performed some
> operations that are like Fourier transform. I got new coordinates that
> were not equally spaced. So I made a grid, and interpolated the
> results I had to that grid. Then I performed ifft. I got an image that
> is similar to my original image, but not in the right coordinates. For
> example, If in the original I had a point in the upper right corner,
> in the new image it is in the middle of the image. What do I need to
> do in order to get back my true image? How is it related to the
> sampling frequency? 

Hi,

I created an image in Matlab in the following way: I created 2 vectors
that represent the image coordinates, and gave a value to each
combination of the vectors. For example: a=[-0.4:0.02:0.4], b=a,
image(y,x) is the value of a(y), b(x). Then I performed some
operations that are like Fourier transform. I got new coordinates that
were not equally spaced. So I made a grid, and interpolated the
results I had to that grid. Then I performed ifft. I got an image that
is similar to my original image, but not in the right coordinates. For
example, If in the original I had a point in the upper right corner,
in the new image it is in the middle of the image. What do I need to
do in order to get back my true image? How is it related to the
sampling frequency?