This version of GFourier is able to work only on grayscaled images without alpha channel.

Right-click on any image of this type and select Filters/Enhace/Fourier; this will start GFourier. You can perform a selection on the image before, and GFourier will only act on the selected zone. However, GFourier will internally work with the smallest rectangle containing the selected area (GIMP's plug-ins common behavior).

First of all, GFourier must calculate the Fourier Transform of the image, where each pixel of the image is considered to be an element of a real matrix; the Fourier Transform is then applied to this matrix. These transforms involve lots of calculations and may require some time; a progress bar will appear on screen. In case that you did not compile GFourier with FFTW support (see GFourier and FFTW for more information), a FFT algorithm will be used with images of dimensions that are powers of two, and a slower general algorithm with other dimensions.

Now, GFourier's main window will appear. It presents the results of the Fourier Transform and allows the user to apply filters, transform the data or calculate several operations.

Later, GFourier will calculate the Inverse Fourier Transform of the data. Because this inverse transform produces complex numbers, the module of the results is calculated. Optionally, this module is normalized or equalized; finally, it is converted to integer to produce an image.

Main window

GFourier's main screen contains a menu bar at the top, several buttons at the bottom and a preview at the center.

The preview represents the data which results from the Fourier Transform. It is a gray bitmap where black pixels stand for zero-module vectors and white ones for vectors of maximum module. The scale used in this conversion is adjusted each time that the data is modified; this way, the full range of gray values is always used on each representation. The View/Invert options exchanges the meaning of black and white, and the View/Contrast option modifies the contrast. You can also choose what is this representation showing: the real part of each point, its imaginary part or the module; that is the View/Type option.



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