vfft − Fast Fourier Transform (FFT)

vfft [if=<infile>] [of=<ofile>] [-i] [-r] [-c] [-m]

Vfft computes the FFT of the image. All computations are conducted in single precision floating point arithmetic and the result is a two channel (real, imaginary) image. By default the input is modulated so that the origin of the frequency domain is located in the center of the image. The FFT is computed separately on the rows and the columns. Each one-dimensional FFT (or inverse FFT) operation is weighted by 1/sqrt(n).

The image dimensions must be a power of two. All image types except index are accepted for input.

if=<infile>

the if= parameter specifies the input file.

if=<infile>

the of= parameter specifies the output file.

-i

The -i option specifies the Inverse FFT operation.

-m

The -m option inhibits the modulation by -1**i; therefore, the zero frequncey term is located at image location (0,0).

-r

The -r option specifies that the FFT of the rows only is to be computed. By default the two-dimensional FFT is computed.

-c

The -c option specifies that the FFT is of the columns only is to be computed. By default the two-dimesional FFT is computed.

A. P. Reeves, 10/78, 2/98