how to perform 2dft with zero padding

[Sundar...]

hai ,

i am quiet new to labview functions
could any one help me how to perform
fft of 2d functions with zero padding
specific to image functions

a function similar to
fft2(image,size,size)

that is performed in matlab
i would need these functions with
respect to image functions,

it would very helpfull if u could also tell me
how to perform correlation also with zero
padding of 2d functions

and i would like to know how to resize an image
with zero padding
example:
i need to place a 200*200 image into an
500*500 image resolution at (0,0)
and every else it has to be padded with zeros
execpt the image

[Scott_R]

Hello,

It sounds like you will need to make use of the IMAQ ImageToArray and ArrayToImage functions. Do you have NI-IMAQ or the NI Vision Development Module installed on your system? The NI-IMAQ driver is a free download available at:

NI-IMAQ Version 3.1.1 for Windows 2000/NT/XP
http://digital.ni.com/softlib.nsf/websearch/E289F96B03BDD2AC86256FCB0078B178?opendocument&node=132060_US

The Vision Development Module is a software package that must be purchased. The NI-IMAQ driver provides the functionality to convert an image into a 2-D array. The Vision package provides the functions to convert from a 2-D array back into an image. This would be useful in performing the zero-padding that you referred to earlier. You could convert your 200x200 image into an array and then copy that array into a larger array of zeroes and then convert the larger array into an image.

The Vision Development module has two functions (IMAQ Correlate and IMAQ FFT) that you could use to perform your image analysis. If you have the Vision Development Module, you can locate these VIs by opening the function palette and navigating to:

All Functions >> NI Measurements >> Vision >> Image Processing >> Filters
All Functions >> NI Measurements >> Vision >> Image Processing >> Frequency Domain

You could also convert the image into a 2-D array and then use the signal analysis VIs to perform the same task.

If you have any questions about these IMAQ or Vision VIs, please let me know.

Regards,
Scott R.
Applications Engineer
National Instruments