vol.subsampling {espadon}

Subsampling a volume

Description

The vol.subsampling function sub-samples the grid of a "volume" class object.

Usage

vol.subsampling(
  vol,
  fact.ijk = 2,
  interpolate = TRUE,
  method = c("NN", "Av"),
  alias = "",
  description = NULL
)

Arguments

vol

"volume" class object.

fact.ijk

Strictly positive integer, or a vector of 3 strictly positive integers.

interpolate

Boolean, default to TRUE.

method

method of interpolation, defaulted to 'NN' ie 'Nearest Neighbor'. See Details.

alias

Character string, $alias of the created object.

description

Character string, describing the the created object. If description = NULL, it will be paste ("subsampling" ,vol$description).

Details

The interpolation method is chosen from:

• 'NN': the value of a voxel is calculated from its nearest adajcent neighbors.

• 'Av': the value of a voxel is the weighted average of the voxels contained in a box, whose sides are automatically calculated from the back.bol$dxyz steps.

Value

Returns a "volume" class object, in which 3D volume grid is subsampled: the voxel size is multiplied by fact.ijk and the center location of the volume is invariant.

See Also

vol.oversampling.

Examples

vol <- vol.create(n.ijk = c(10,10,1),dxyz = c(2,2,2), ref.pseudo = "ref1", 
                  modality ="test", pt000 = c(0,0,0))
vol$vol3D.data[] <- array(1:prod(vol$n.ijk), dim = vol$n.ijk)
vol$max.pixel <- prod(vol$n.ijk)
vol$min.pixel <- 1
mid <- as.numeric (apply (get.extreme.pt (vol), 1, mean))
vol_ss <- vol.subsampling (vol, fact.ijk= 2)
mid_ss <- as.numeric (apply (get.extreme.pt (vol_ss), 1, mean))
display.plane(vol,interpolate = FALSE, view.coord = mid[3], 
              abs.rng = c(-5,25), ord.rng = c(-5,25), bg="green")
points (mid[1], mid[2], pch=16, col="red")
display.plane(vol_ss,interpolate = FALSE, view.coord = mid_ss[3], 
              abs.rng = c(-5,25), ord.rng = c(-5,25), bg="green")
points (mid_ss[1], mid_ss[2], pch=16, col="red")