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 | z0 zf | x0 y0 | nx ny | nxpad nypad
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In this field, the user should give the initial and final sections to be filtered.
This field represent the coordinates of the lower left corner of the selected region to be studied.
Here the user gives the sizes (number of pixels) in x and y of the selected region. nx and ny 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 and nypad pixels, in such a way that it becomes periodic in x and y. If the entire image is filtered, the default for nxpad and nypad 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.