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<head><title>Frequency Based</title></head>
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<H3>Frequency Based</H3>
These commands perform Fourier and inverse Fourier transformations of
images. By default, the transformations will automatically convert
images between Fourier to natural orders as expected. For example, <TT>2-D FFT</TT>
will transform the points into natural order after the Fourier transform.
Similarly the inverse, <TT>2-D IFFT</TT>, will reorder the points from
natural order to Fourier order before applying the inverse Fourier transformation.<P>
As you would expect, images that undergo frequency filtering will be complex-valued
after than filtering. Only the real component is shown by <TT>CTSim</TT>. However, <TT>CTSim</TT> does
have options for converting a complex-valued image into a real-valued image via
the <TT>Magnitude</TT> and <TT>Phase</TT> filtering commands.<P>
The available frequency-based filtering commards are:<P>
<UL>
<LI> 2-D FFT
<LI> 2-D IFFT
<LI> FFT Rows
<LI> IFFT Rows
<LI> FFT Columns
<LI> IFFT Columns
<LI> 2-D Fourier
<LI> 2-D Inverse Fourier
<LI> Shuffle Fourier to Natural Order
<LI> Shuffle Natural to Fourier Order
<LI> Magnitude
<LI> Phase
</UL>
<P>
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