/*****************************************************************************
*                                                                            *
*   FFT2.SPL     Copyright (C) 1998-2000 DSP Development Corporation         *
*                               All Rights Reserved                          *
*                                                                            *
*   Author:      Randy Race                                                  *
*                                                                            *
*   Synopsis:    Performs 2D FFT of an input array                           *
*                                                                            *
*   Revisions:   12 Mar 1998  RRR  Creation                                  *
*                13 Oct 1999  RRR  1D case                                   *
*                19 May 2000  RRR  optional lengths                          *
*                                                                            *
*****************************************************************************/

#if @HELP_FFT2

    FFT2

    Purpose: Calculates the 2D FFT of an array

    Syntax:  FFT2(array, rowlen, collen)

              array - a multi-column series

             rowlen - optional intger, FFT row size, defaults to
                      numrows(a)

             collen - optional integer, FFT column size, defaults to
                      numcols(a)


    Returns: A complex array

    Example:
             Fft2({{1, 2}, {3, 4}})

             returns the complex array {{10+0i, -2+0i},
                                        {-4+0i,  0+0i}}

    Remarks:
             FFT2 is often used in image processing applications.
             Use FFTSHIFT to flip the output so the 0 frequency is in
             the center of the plot.

             If the input data is a series (i.e. a single column), a 1D FFT
             is performed.


    See Also
             FFT
             IFFT2

#endif


/* 2D FFT */
fft2(a, rowlen, collen)
{
        if (argc < 3)
        {
                if (argc < 2)
                {
                        if (argc < 1) error("fft2 - input array required");
                        rowlen = numrows(a);
                        collen = numcols(a);
                }
                else
                {
                        collen = numcols(a);
                }
        }
        
        if (numcols(a) > 1)
        {
                /* amazingly simple one liner */
                return(transpose(fft(transpose(fft(a, rowlen)), collen)));
        }
        else
        {
                return(fft(a, rowlen));
        }
}