Jan Eglinger

This is essentially a duplicate (or a slight extension) of https://github.com/imagej/imagej-ops/issues/547.

See the forum topic [Extract all pixels having certain value (IJ2 ops)](http://forum.imagej.net/t/extract-all-pixels-having-certain-value-ij2-ops/9912?u=imagejan) for some discussion that might be related to this issue.

It would be great if use cases like [this one from the forum](http://forum.imagej.net/t/vertical-caliper-distance/9879/10?u=imagejan) could be made super easy. Instead of: ```groovy #@ Dataset input #@ OpService ops sumOp = ops.op("sum",...

@bnorthan wrote: > I could also modify the min, and median op Only the `min` and `max` ops should be changed accordingly. For the median, it makes sense to return...

Thanks to both of you for working on this! 😄 > After all, we always return `DoubleType`, no? The namespace defines the contract, and there could possibly be ops _implementations_...

Agreed. For the mean of an `Img`, I would expect to get a `DoubleType` between `0.0` and `1.0` ideally. How about always returning double in case of `mean`, but always...

Isn't this the same as *Solidity* then? See here: https://github.com/imagej/imagej-ops/blob/master/src/main/java/net/imagej/ops/geom/AbstractSolidity.java#L61 In theory, the convex hull _surface_ (or _boundary_) should always be smaller than the object's _surface_, so the ratio is...

I know this is a bit of a different terrain, but this issue reminds me of https://github.com/scijava/scijava-common/issues/295.

Interestingly, the following both work: ```python >>> jl[:] >>> print(jl[:]) [1, 3, 5, 7, 9] ``` ```python >>> nl = list(pl) >>> nl[:] [1, 3, 5, 7, 9] ```

Probably would require copying the `slice` logic from here: https://github.com/jpype-project/jpype/blob/8a32c42373ca10e0aa587d5fab0065dab52f94c6/jpype/_jcollection.py#L89-L96 @ctrueden what's the reason we still have `JavaCollection`, `JavaList` etc. in `scyjava`? Is there additional functionality to what JPype brings?