# 2.1.22.2.1.15 fft_2d_real

## Description

Performs nFFTRow*nFFTCol-point discrete 2D Fourier transform or 2D inverse Fourier transform.

## Syntax

int fft_2d_real( int nFFTRow, int nFFTCol, matrix<complex> & mSig, FFT_SIGN iSign = FFT_FORWARD )

## Parameters

nFFTRow
[input] the number of rows to do Fourier transform.
nFFTCol
[input] the number of cols to do Fourier transform.
mSig
[modify] Input: for forward transform, it contains real signal to be transformed.
for backward transform, it contains complex signal.
Output: for forward transform, it contains the complex signal of 2D DFT.
for backward transform, it contains the real signal of 2D IDFT.
iSign
[input] FFT_FORWARD: FFT; (by default)
FFT_BACKWARD: IFFT.

## Return

Returns 0 for success or error codes for failure.

## Examples

Prior to compilation, load fftEx_utils.c to the workspace by executing the following LabTalk command:

Run.LoadOC("Originlab\fftEx_utils.c", 16);

To retain fftEx_utils.c in the workspace for successive sessions, drag and drop the file from the Temporary folder to the System folder.

EX1

#include <fftex_utils.h>
void fft_2d_real_ex1()
{
matrix<complex> sig(2, 2);
for (int ii=0; ii<2; ++ii)
for (int jj=0; jj<2; ++jj)
{
sig[ii][jj].m_im = (ii+jj)%2;
sig[ii][jj].m_re = !sig[ii][jj].m_im;
}
for (ii=0; ii<2; ++ii)
{
for (int jj=0; jj<2; ++jj)
printf ("%lf+%lfi\t", sig[ii][jj].m_re, sig[ii][jj].m_im);
printf ("\n");
}
printf ("\n");
fft_2d_real(2, 2, sig, FFT_BACKWARD);
printf ("\n");
for (ii=0; ii<2; ++ii)
{
for (int jj=0; jj<2; ++jj)
printf ("%lf+%lfi\t", sig[ii][jj].m_re, sig[ii][jj].m_im);
printf ("\n");
}
}

## Remark

Performs nFFTRow*nFFTCol-point discrete 2D Fourier transform or 2D inverse Fourier transform.

mSig will be padded with zeros if it has less than nFFTRow*nFFTCol points and truncated if it has more.

For forward FT, the input is real data, and the output is complex data;

For backward FT, the input is complex data, and the output is real data.

fftEx_utils.h