Transformation

[Mathew]

I am having an image of , say M X N Pixel size. At first I have to do a 2 D Fast Fourier Trnasformation of this image. Then an Interpolation and finally back an Inversve Fourier Transformation.

I have first tried to read the image from a folder path. Changed it to pixelmap and extracted the X & Y Resolution of the image. Now how can i do the rest. Is the X & Y resolution directly be given to the 2 D FFT function? COuld you please help me with this?

(I would prefer not to use any IMAQ functions.)

Thanks

[osvaldo]

Hi Mathew;

I'm not well experienced with image processing, but in the past I would find some interesting things on this web site:

http://homepages.inf.ed.ac.uk/rbf/CVonline/transf.htm

A good compendium on algorithms and even some teoretical explanations.

Osvaldo

[OlivierL]

Hi Mathew,

Check the code below to have an idea of how to do it. It's not too complicated. Don't be surprised with the "weird" numbers at the end, they round up to the exact initial values.

Cheers,

Olivier

[Mathew]

QUOTE (OlivierL @ Oct 30 2008, 05:00 PM)

Hi Mathew,

Check the code below to have an idea of how to do it. It's not too complicated. Don't be surprised with the "weird" numbers at the end, they round up to the exact initial values.

Cheers,

Olivier

--------------------------------------

Hello Olivier

Thank you for the example. I tried to do the work replacing the input array by an pixel array from an array. But towards the end part of your VI , i didnt understand the use of (x+2y) ? What is the use of that one?

thnksss

QUOTE (osvaldo @ Oct 30 2008, 02:45 PM)

Hi Mathew;

I'm not well experienced with image processing, but in the past I would find some interesting things on this web site:

A good compendium on algorithms and even some teoretical explanations.

Osvaldo

------------------------------------------------------------------

Hello Osvaldo

I cannot find anything on the link you gave.. i think its not working anymore...

Thankss

[OlivierL]

--------------------------------------

Hello Olivier

Thank you for the example. I tried to do the work replacing the input array by an pixel array from an array. But towards the end part of your VI , i didnt understand the use of (x+2y) ? What is the use of that one?

thnksss

------------------------------------------------------------------

x+y 2 is just the default name LabVIEW gave to the result of the addition. There is nothing special there other than adding and dividing by two (since you are doing your operation on two copies of the same array, only in different orientation, row and column). This means that you need to do your interpolation on both "branches" of the code if you want it to be done in both dimensions and then merge those results together. I hopw this is a bit more clear now.

In my example, X and Transposed array are the individual results of your treatment in both dimensions, prior to being joined back together. Both treatment could potentially be done sequentially instead of in parallel and the results in one of the dimensions would be more accurate! *** Actually, as I realize it, this might be a better solution for interpolation, to go in one dimension first, then transpose and treat the second dimension. It will definitely save you time and trouble because your array sizes won't match in parallel. ***

Cheers,

Olivier

[Mathew]

QUOTE (OlivierL @ Nov 3 2008, 04:38 PM)

--------------------------------------

Hello Olivier

Thank you for the example. I tried to do the work replacing the input array by an pixel array from an array. But towards the end part of your VI , i didnt understand the use of (x+2y) ? What is the use of that one?

thnksss

------------------------------------------------------------------

x+y 2 is just the default name LabVIEW gave to the result of the addition. There is nothing special there other than adding and dividing by two (since you are doing your operation on two copies of the same array, only in different orientation, row and column). This means that you need to do your interpolation on both "branches" of the code if you want it to be done in both dimensions and then merge those results together. I hopw this is a bit more clear now.

In my example, X and Transposed array are the individual results of your treatment in both dimensions, prior to being joined back together. Both treatment could potentially be done sequentially instead of in parallel and the results in one of the dimensions would be more accurate! *** Actually, as I realize it, this might be a better solution for interpolation, to go in one dimension first, then transpose and treat the second dimension. It will definitely save you time and trouble because your array sizes won't match in parallel. ***

Cheers,

Olivier

----------------------------

Hello Olivier

Thanks. BUt i have one more problem now. I am now trying to do the 2D - FFT in another approach. Firstly I need to compute the FFT for rows (in parallel) and then the FFt transforms for the columns of the result. Then i have to map the samples of the final FFT from cartesian coordinate system to polar ones. How could this be implemented?

Thanks