Posted by
Kenneth Sloan-2 on
URL: http://imagej.273.s1.nabble.com/Hyperstack-with-nz-1-problem-tp5019980p5020060.html
I respectfully disagree.
First, I think it's preferable to consider pixels as having area, and voxels as having volume (this view is supported by the display shown when images are zoomed). Indeed - this was usually part of the content in the first class meeting for every course in image processing (or raster graphics) that I taught over the course of 40 years.
Second, I think it's preferable for it to be possible to view a slice as a volume which simply has zero extent in the z-direction. I'd actually prefer it to be considered to have some finite depth (when viewed as a volume) rather than 0.0, but, alas, there is no easy way to assign that finite depth. Once you have two slices, and a spacing between them, I prefer to think of each slice as having a finite depth (a slab, rather than a plane).
Most of the time, it's reasonable to take the point of view that a pixel = a point (rather than an area) and a voxel = a point (rather than a volume), but I think it's preferable to ALLOW both points of view.
I see nothing problematic about a 3d volume consisting of a single slice.
If you think a pixel is a point - do you consider a SINGLE pixel to be a 1x1 image? or it that "not an image"?
I, for one, would be pleased if ImageJ were to allow this point of view (A volume with x*y*1 voxels). But, for now, the answer for the OP is: ImageJ just doesn't allow that point of view. I think it's a deficiency.
--
Kenneth Sloan
[hidden email]
Vision is the art of seeing what is invisible to others.
> On 9 Feb 2018, at 12:03 , Herbie <
[hidden email]> wrote:
>
> Good day!
>
> "[...] so that ImageJ treats a single slice as a volume?"
>
> A slice is an image!
>
> A slice has no extension orthogonal to itself.
> A pixel also has no extension in any direction because it is a mathematical
> point in 2D, i.e. a number or sample value.
> A voxel also has no extension in any direction because it is a mathematical
> point in 3D, i.e. a number or sample value.
>
> Pixels, i.e. values at points in 2D, are arranged in a 2D grid and the
> sometimes equidistant *spacing* of the grid points is often confused with
> the pixel size, that actually doesn't exist.
> (A pixel doesn't have a size.)
>
> Voxels, i.e. values at points in 3D, are arranged in a 3D grid and the
> sometimes equidistant *spacing* of the grid points is often confused with
> the voxel size, that actually doesn't exist.
> (A voxel doesn't have a size.)
>
> In short:
> A slice has no neighbors orthogonal to itself, i.e. there is no (defined)
> spacing in the third dimension.
>
> That said, you may indeed use dummy slices to define the missing spacing!
>
> HTH
>
> Herbie
>
>
>
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