[Feat] Add JSON output to r.describe

[NishantBansal2003]

Add JSON output for easy parsing of r.describe output.

Describe the solution you'd like
Add an option for format, such as format=plain for the current output format and format=json for the JSON output.

A possible JSON layout could be:

[
  {
    "values": "0.996534-8.677654"
  },
  {
    "values": "8.677654-16.358774"
  },
  {
    "values": "16.358774-24.040000"
  }
]

Describe alternatives you've considered
Alternatively(helpful for numerical operations or parsing), the JSON layout could look like this:

[
  {
    "min": "0.996534",
    "max": "8.677654"
  },
  {
    "min": "8.677654",
    "max": "16.358774"
  },
  {
    "min": "16.358774",
    "max": "24.040000"
  }
]

[NishantBansal2003]

Hey @echoix, I was trying to write tests for the above change, and I am using this raster map:

map = if(row() == 5 && col() == 5, null(), if(row() % 2 == 0, col() * 0.5, -col() * 0.5))

When I run the following command:

r.describe -1 map

I get the following output:

*
-5.000000--4.960784
-4.529412--4.490196
-4.019608--3.980392
-3.509804--3.470588
-3.039216--3.000000
-2.529412--2.490196
-2.019608--1.980392
-1.549020--1.509804
-1.039216--1.000000
-0.529412--0.490196
0.450980-0.490196
0.960784-1.000000
1.470588-1.509804
1.941176-1.980392
2.450980-2.490196
2.960784-3.000000
3.431373-3.470588
3.941176-3.980392
4.450980-4.490196
4.960784-5.000000

Is this output format correct(for negative values)? Also, when should we use the "-" symbol and "thru" in the r.describe output?

[echoix]

Can another "expert" or someone knowing r.describe jump in? I don't know what to answer here

[neteler]

The thru of r.describe is understood by e.g. r.reclass and other commands. Hence, it is the official syntax (yes, looks oldish but works since ~1984).

The output of r.describe is also (to remain) machine readable:

ag --python r.describe
scripts/d.rast.leg/d.rast.leg.py
123:    cats = gs.read_command("r.describe", map=map, flags="1n")

scripts/r.grow/testsuite/test_r_grow.py
61:        shrined_range = SimpleModule("r.describe", flags="i", _map=self.mapShrunkNoNULL)

gui/wxpython/rdigit/controller.py
466:                        "r.describe", flags="1n", map=name, quiet=True

Of course, with increasing JSON support we get modern options here.