VDIRF

vdirf − directional mean or median smoothing filter.

vdirf if=<input> ig=<mask> of=<output> c=<> -a

vdirf vdirf performs directional filtering in the masked region (ig=). For each voxel, a 3x3x3 cube centered at that voxel is divided evenly into 3 groups with each group containing 9 voxels. There will be 9 such grouping methods. For each method, there will be a group of voxels in the center (group L) and two groups on each side (H1 and H2). Each group has a mean intensity value (Lu, H1u and H2u). A function is used to calculate a score for each grouping method and the grouping with the maximum score is chosen. In the chosen grouping, filtering (default is mean and -a specifies median) is performed in the L group and the value is assigned to the center voxel. c= specifies the score function F: if c=1, F=H1u+H2u-2*Lu (default); if c=2, F=-Lu; if c=3, F=-variance(L).

Input if= is the intensity image and ig= is the mask. The output of= is the filtered image. c= is the option to choose different criteria in selecting the voxel group. -a is the option to perform median filtering in the selected group (default is mean).

vdirseg(1)

Y. Xie