Documentation on fft

Task: fft
Purpose: Fourier transform on image(s)
Categories: uv analysis, map making

        FFT is a MIRIAD task which performs a fast Fourier transform on
        an image. If the input is a cube, then each plane is FFT'ed
        individually (i.e. this does not perform a 3D FFT).

        Blanked pixels in the input images are treated as if the pixel
        was zero.
        If the input image is not a power of two in side, the image is
        blank padded up to a power of two.

        The output of the FFT would normally be complex valued. You can
        save the output in any one of several ways -- as the real or
        imaginary part, or as the magnitude (amplitude) and phase.

Key: rin
        This gives the input real part image. No default.

Key: iin
        This gives the input imaginary part image. The default is a zero image.

Key: sign
        This gives the sign of the exponent in the transform. -1 gives a
        forward transform, +1 an inverse transform. An inverse transform
        applies 1/N scaling. The default is a forward transform.

Key: center
        This gives the origin of the transform. If two values are
        given, then they are used as the origin in the x and y axis
        respectively. If one value is given, then this is used for the
        origin for both the x and y dimensions. The default is the
        header value for CRPIX1 and CRPIX2 (if they are in the header) or
        N/2+1 (if CRPIX is missing from the header).

Key: rout
        The output real part image. The default is not to write this image out.

Key: iout
        The output imaginary part image. The default is not to write this
        image out.

Key: mag
        The output magnitude (amplitude) image. The default is not to write
        this image out.

Key: phase
        The output phase image. The default is not to write this image out.