Author: Bob Dougherty (firstname.lastname@example.org) Installation: Download Swap_Quadrants_3D.java or Swap_Quadrants_3D.class and place it in the Plugins folder. Description: ImageJ plugin to perform a 3D "quadrant swap" operation. This changes the order of the Hartley coefficients in a 3D FHT image stack to switch from the native order (low frequencies on the outsides) to the more-convenient order for viewing and manipulation (high frequencies on the outsides). Running the plugin a second time restores the the native order. One use would be to start with a regular, spatial domain, image stack and apply FHT3D to convert to the Hartley transform. The results appear in the native order. Use Swap_Quadrants_3D to convert to the alterate order. Modify the spectral coefficients in some way, perhaps using frequency-by-frequency multiplication by a filter function. Reverse the quadrant-swap by running Swap_Quadrants_3D again. Finally, make another call to FHT3D to return to the spatial domain.
This version of Swap Quadrants differs from the one in ImageJ in several ways. It operates in 3D; the slices of the stack are swapped along with the quadrants of the images. Also, the dimensions of the images are not restricted by this plugin. FHT3D does require the horizonal and vertical dimensions be powers of 2, but they need not match.
Versions: 0: 5/03/2006 License:
Copyright (c) 2006, OptiNav, Inc.
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