Wrap grdmix

[weiji14]

Description of proposed changes

Wrapping the grdmix function which does "Blending and transforming grids and images". For a GMT example, see https://docs.generic-mapping-tools.org/6.2/gallery/ex52.html

Parameters/Aliases to wrap:

• A alpha/transparency?
• C construct
• D deconstruct
• E boundary
• G outgrid
• I shading/intensity?
• M monochrome
• N normalize
• Q opaque
• R region
• V verbose
• W weights
• f coltypes

The initial implementation here will focus on the construct -C and deconstruct -D methods. Construct involves taking e.g. 3 grids and turning them into 1, whereas deconstruct turns 1 image into 3 separate RGB files (there are a few other possible combinations like 2-band and 4-band inputs but let's not go there yet).

In a pure xarray world, 'construct' would turn an xarray.DataArray of shape (3, 180, 360) to (1, 180, 360) suitable for plotting using grdimage. The 'deconstruct option seems less useful in real life, but it does allow us to turn the @earth_day_01d.tif file into 3 separate files to be 'construct'ed later 🙂

First part of addressing #578, closes #370.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[willschlitzer]

@weiji14 Are you planning on getting this into v0.5.0?

[weiji14]

@weiji14 Are you planning on getting this into v0.5.0?

I was, but there's some complication with the API design (see #1555), so might need to move it to v0.6.0.