Compute, over all images in a stack along an axis, the foreground and background pixels as a binary mask. A pixel is a `foreground` pixel iff its value is greater than the `threshold` parameter in at least one of the slices. A pixel is a `background` pixel iff its value is below or euqal to the `threshold` in all slices.
vol.boundary.mask(volume, plane = 1L, threshold = 0L)a 3D image volume
integer vector of length 2 or something that will be turned into one by vol.plane.axes.
numerical, the threshold intensity used to separate background and foreground. All voxels with intensity values greater than this value will be considered `foreground` voxels.
integer 2D matrix with dimensions of a slice of the volume. Positions set to 1 are `foreground` pixels and positions set to 0 are `background` pixels (see `Details` section).