Support for custom colormap in precipfield.py and plot_custom_precipitation_range.py example

[rutkovskii]

[MODIFY] Add support for custom colormap configuration in precipfield.py

This update allows user-defined ranges and colors for plots. It supports
intensity (tested) and depth (untested), but not probability. A private
function was added to validate the colormap provided by the user.

[ADD] Add plot_custom_precipitation_range.py example demonstrating how to
create a custom config and use it for plotting.

Note: As mentioned, it should work with depth, but I have not verified it.

#430

[dnerini]

Hi there, thanks for the reminder. I'll try to have a close look today, I don't expect any major issue.

[codecov]

Codecov Report

Attention: Patch coverage is 21.73913% with 18 lines in your changes missing coverage. Please review.

Project coverage is 83.89%. Comparing base (ee60fa6) to head (a12df02).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pysteps/visualization/precipfields.py	21.73%	18 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #433      +/-   ##
==========================================
- Coverage   84.00%   83.89%   -0.11%     
==========================================
  Files         160      160              
  Lines       12882    12900      +18     
==========================================
+ Hits        10821    10822       +1     
- Misses       2061     2078      +17     

Flag	Coverage Δ
unit_tests	83.89% <21.73%> (-0.11%)	⬇️

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[dnerini]

@rutkovskii thanks for your contribution! I very much appreciated the clean implementation and the effort in adding a clear example of this new feature, way to go!

Please just remove the final line from the example when you save the figure, and then we'll be ready to merge!

[dnerini]

We usually do not include the code for downloading the example data in the other examples, since the data are downloaded before running the example codes, but I'm OK with leaving this snippet ;-)

[rutkovskii]

Sounds good, I'll keep it as is. My thought process was that the data erequires a manual download, so providing a way for users to quickly see how the plotting works in case they do not have it loaded.
Is the data included in the installation of the library via pip?

[dnerini]

no, the data are not part of the actual package, but we provides some tools to get them (as the functions you used), see https://pysteps.readthedocs.io/en/stable/user_guide/example_data.html

[rutkovskii]

@dnerini I made the change. You can merge as you are the authorized user.