downsampleAllenVolume Downsamples a 3D volume by a specified ratio

Syntax

Vdownsampled = downsampleAllenVolume(V, ratio)
Vdownsampled = downsampleAllenVolume(V, ratio, fillVal)
[Vdownsampled, Vresampled] = downsampleAllenVolume(___)

Description

Vdownsampled = downsampleAllenVolume(V, ratio) returns a downsampled version of V containing every nth slice (in every dimension) based on the specified ratio.

Vdownsampled = downsampleAllenVolume(V, ratio, fillVal) returns a downsampled version of V and allows specifying a fill value for the resampled volume.

[Vdownsampled, Vresampled] = downsampleAllenVolume(_) returns both the downsampled volume and a resampled version of V where the nth slices are kept, and the other elements are set to a specified fill value (default is NaN).

Examples

V = downsampleAllenVolume(getAllenStructure(703, 50, 2), 2);
[Vdownsampled, Vresampled] = downsampleAllenVolume(getAllenStructure(703, 50, 2), 2, 0);

Input Arguments

V - Input 3D volume (numeric array)

ratio - Downsampling ratio (positive integer) Specifies the step size for downsampling in each dimension.

fillVal - Fill value for resampled volume (numeric scalar | NaN (default)) Specifies the value to fill in the resampled volume for elements not included in the downsampling.

Output Arguments

Vdownsampled - Downsampled volume (numeric array) Contains every nth slice of the input volume V in each dimension.

Vresampled - Resampled volume (numeric array) Contains the nth slices of the input volume V, with other elements set to the specified fill value.

Usage Notes

The function assumes the input volume V is a 3D numeric array.
The Allen downsampling always starts from the 1st index (in PIR format).

Authors

Mehul Gajwani, Monash University, 2025