This program calculates the Fourier transform (FT) of the image that is open. The displayed FT is in logarithm scale. One can calculate the FT of the entire image, or of a selected region of it.
Overview | x0 y0 z0 | nx ny nz | nxpad nypad nzpad
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This field represent the coordinates of the lower left corner of the selected region to be studied (z0 is the first section of the selected region).
Here the user gives the sizes (number of pixels) in x, y, and z of the selected region. nx, ny, and nz must be an integer power of 2, less or equal to 2048.
Since the FT expansion assumes that the image is periodic we pad the image with nxpad, nypad, and nzpad pixels, in such a way that it becomes periodic in x, y, and z. If the Fourier transform of the entire image is calculated, the default for nxpad, nypad, and nxpad is the smallest value that brings the size of the image to the next power of two. If a selected region of the image is studied, then the default value is 10% of the number of pixels in the respective direction.