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Basic Information 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.