erode: potential bug with 3D strel_diamond

[korbinian90]

I'm using the erode function with a diamond shape structuring element, but the output doesn't look like what I expected. I'm working with 3D masks. Here is a minimal example with 3x3x3 showing the unexpected result.

Explanation:
The center voxel image[2,2,2] should be 0 after erosion (It is connected to image[2,2,3]==0).
In the output of erode, the voxel eroded[2,2,2]==1 though, which is not what I expected.

julia> image = [1 1 1; 1 1 1; 1 1 1;;; 0 1 0; 1 1 1; 1 1 1;;; 0 0 0; 0 0 0; 1 1 1]
3×3×3 Array{Int64, 3}:
[:, :, 1] =
 1  1  1
 1  1  1
 1  1  1

[:, :, 2] =
 0  1  0
 1  1  1
 1  1  1

[:, :, 3] =
 0  0  0
 0  0  0
 1  1  1

julia> SE = strel_diamond(box)
3×3×3 ImageMorphology.SEDiamondArray{3, 3, UnitRange{Int64}, 0} with indices -1:1×-1:1×-1:1:
[:, :, -1] =
 0  0  0
 0  1  0
 0  0  0

[:, :, 0] =
 0  1  0
 1  1  1
 0  1  0

[:, :, 1] =
 0  0  0
 0  1  0
 0  0  0

julia> eroded = erode(image, SE)
3×3×3 Array{Int64, 3}:
[:, :, 1] =
 1  1  1
 1  1  1
 1  1  1

[:, :, 2] =
 0  1  0
 0  1  0
 1  1  1

[:, :, 3] =
 0  0  0
 0  0  0
 0  0  0