add ability to burn feature field values to raster

[solomon-negusse]

Hi @dcherian, we often need to burn some numeric field values when rasterizing vectors. This is a draft implementing that for rasterio engine if there is interest to adopt it. It works now but need to do some cleaning up. I see rusterize supports this as well and can take a stab at adding that too.

[dcherian]

I'm inclined to treat this as an application of indexing or xr.where.

The default choice of using len(geometries) as a fill value bites us though. Maybe we should change that.

import xarray as xr
import xproj  # noqa
import geodatasets
import geopandas as gpd

ds = xr.tutorial.open_dataset("eraint_uvz")
ds = ds.proj.assign_crs(spatial_ref="epsg:4326")

world = gpd.read_file(geodatasets.get_path("naturalearth land"))


from rasterix.rasterize import rasterize

n = rasterize(ds, world[["geometry"]], xdim="longitude", ydim="latitude", engine="rasterio")
n.plot()

Use where to create the right indexer, and then index the dataframe

n = xr.where(n != len(world), n.astype(int), -1)
world["featurecla"].to_xarray()[n]