Apply a bilateral filter to a volumetric image — bilateral

This function smooths a volumetric image (3D brain MRI data) using a bilateral filter. The bilateral filter considers both spatial closeness and intensity similarity for smoothing. Only in-mask, in-bounds neighbors contribute to each local weighted average.

Usage

bilateral_filter(
  vol,
  mask,
  spatial_sigma = 2,
  intensity_sigma = 1,
  window = 1,
  range_scale = NULL
)

Arguments

vol: A NeuroVol object representing the image volume to be smoothed.
mask: An optional LogicalNeuroVol object representing the image mask that defines the region where the filtering is applied. If not provided, the entire volume is considered.
spatial_sigma: A numeric value specifying the standard deviation of the spatial Gaussian kernel (default is 2).
intensity_sigma: A numeric value specifying the standard deviation of the intensity Gaussian kernel (default is 1).
window: An integer specifying the number of voxels around the center voxel to include on each side. For example, window=1 for a 3x3x3 kernel (default is 1).
range_scale: Optional positive numeric range scale used by the intensity kernel. If NULL, the scale is estimated as the standard deviation of the current input values inside mask. Supply a fixed value to apply the same range bandwidth across observed and null maps.

Value

A smoothed image of class NeuroVol.

Examples

brain_mask <- read_vol(system.file("extdata", "global_mask_v4.nii", package="neuroim2"))

# Apply bilateral filtering to the brain volume
filtered_vol <- bilateral_filter(brain_mask, brain_mask, spatial_sigma = 2,
intensity_sigma = 25, window = 1)