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02/05/2008

FFT Tool

Notes Levy Density Function

The Fast Fourier Transform Tool is also accessed via the Filter menu in the menu bar. It is the bottom one in the list.

The FFT is done using Fourier / Fourier Transform.

 

Complex image input and output.

Complex images are saved as are other image types, with File / Save as TIFF, except that the complex images are saved as two TIFF files, <name>-realpart.tif, and <name>-imagpart.tif.  I/O / Open, in the I/O button above, will read both parts and display them as a complex image.  The image will be (complex double-float), that is in double precision, whether or not it is read from double- or single-precision files.  Opening either image with File / Open will open just the real or imaginary part separately.

Depending on the 8-byte float parameter in the File UtilitiesTool ( File / File Utilities ), the real and imaginary parts will be saved as 8-byte floating point numbers (the default), or as 4-byte floating point numbers, if the numbers are within the dynamic range for 4-byte ieee floats, which they generally seem to be.


This is an example of an image and its Fourier transform: