Create position-sensitive map operation about imagej-ops

[ctrueden]

Perhaps more flexibly, the op could take the Localizable (i.e., Cursor or RandomAccessible) itself as its extra argument. Then the op can localize however it wants.

[dscho]

I think it is a useful thing to add, but it is not a "map" operation (which by definition does not care about position so it can be parallelized trivally). We'll need to be careful with naming (maybe Pixelwise?)

[ctrueden]

I don't understand the technical definition of the term "map" enough to agree that this would not be a "map" operation. Do you have a reference?

[dscho]

I guess my understanding was incomplete: https://en.wikipedia.org/wiki/Mapreduce#Map_function. In light of that, I fear that we are really using the term map more in the mathematical sense where it maps inputs to outputs (at least that's my understanding of a mathematical map operation).

[ctrueden]

@dscho: Well, that's only for MapReduce, which is a very a specific thing. Very popular now, so I'm sure it turns up early in Internet searches, but still. I think it was @dietzc who first started using the terms "map" and "mapper"... from whence did these terms come, @dietzc?

[dietzc]

We used the word "map" in our implementations since some years. I think it comes from the mathematical definition of map (http://en.wikipedia.org/wiki/Map_%28mathematics%29, morphism I guess), but honestly I think @hornm came up with the name. I like the name because it's short, easy and understandable. synonyms would be: assign, element-wise (pixel-wise is not general enough) and so on.

about the actual topic in the issue: Yes such an operation would be really useful, but would the "input" of such a map still be an unary function or more a binary function (if we would have something like that?. Currently a map uses a function A,B and applies it e.g. on each pixel (type A to type B). The map @ctrueden describes would take A, Localizable and produce B. So what would the input of such a Map operation be? BinaryFunction A1,A2,B? Of course we would just need the BinaryFunction for faster methods calls inside the op (as we actually could plug in any op and fill its parameters using the injections mechanism).

[ctrueden]

Thanks for the explanation, @dietzc. Personally I am fine with the new operation also being called "map" here unless anyone feels strongly otherwise. I will work on implementing this op later, after our other urgent priorities have been resolved.