Mathew

Hello Everybody... sorry for the late response... I was having tropuble in accesing the site.. I think i need the method which jdunham mentioned... But could you both please explain it in a VI. It would be much clearer then.. thanksss QUOTE (jdunham @ Mar 14 2009, 12:09 AM)

Its a part of my prj wrk...any idea? I have to mapp the points in polar to rectangular.

Suppose we take the red point on the polar grid. When i convert it to Re & Im parts i get a number in rectangular grid, but this point is not actually present in the rectangular grid shown on right. This polar point was found by interpolating some points. How can i find a point in rectangulr grid then? thanks

Hello I am having an image. I converted this image to 2D array. Now i do the polar conversion in this array.Suppose on a polar grid i need values along 6 angles(60,120,180,240,300,360 degrees). I am having a 2D array in Rectangular grid. So i nterpolate values in 2D array and found the required values in polar grid. With these values i perfomed FFT and got a plot. Now i take the peak values from this FFT array and i need to go back in the reverse direction so that i may see as real picture what these peak values look like. So as a first step i do the inverse FFT for these values. What would bethe next step.? How can i get those old points in 2D array from this interpolated values in polar grid? Thanksss See attachmenet to understand the rectangular polar grid system

Hello .. Actually i tried with that.. but that is not the one which i need.I need to interpolate them in polar raster.

I have an NXN image. I made the 2D Fast Fourier Transform of this one. Now i need to binearly interpolate the Fourier complex spectrum in a polar raster. How is this possible.? Thanks

Hello N I have found 2D FFT for an image. Now i need to compute the Central Slices for a particular value of (r,theta). This is what i need and not direct complex to polar conversion. thankss QUOTE (Neville D @ Nov 12 2008, 06:19 PM)

DO anyone know how to apply 2D Central slice theorem for 2D Fourier Transformed Image? FOr this forst we need to mapp the samples of FT in Cartesian coordinate system to Polar. Can anyone help with this? Thanks

Hello I have an image of size M X N (pixel). Fisrt of all i have read the image from the path location. Then I used Unflatten Pixmap VI to convert the image to array. Now i need to find the 2 D FFT. I have to do the FFT by fist computing the transforms of the rows in parallel and then the transforms of the columns of the result. For that i extracted the N Resolution value and gave it to ta for loop ( since there are N rows for the image.) Then I calculated the FFT for these rows. The resulting array is transposed to do the FFT for the columns. Is the VI i made correct? Please see the attchement for the image. How can i get the 2D- FFT plot ? Thankss

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

QUOTE (OlivierL @ Oct 30 2008, 05:00 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 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

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