Utility functions for converting from a row/column index of a raster window, to longitude/latitude or an H3 index. Useful for H3-indexing raster data read with rasterio.

h3_raster_windows.py

#!/usr/bin/env python3
import pyproj
import h3.api.basic_int as h3

# A window_transformation is the affine transformation of a window, see https://rasterio.readthedocs.io/en/latest/topics/windowed-rw.html?highlight=window_transform#window-transforms

# Transformer
transformer = lambda s_srs, t_srs: pyproj.Transformer.from_proj(pyproj.Proj(s_srs), pyproj.Proj(t_srs), always_xy=True)
# Row/column conversion to lon, lat; given a window transformation and pyproj.Transformer
rc2lonlat = lambda r, c, window_transformation, transformer: transformer.transform(*(window_transformation * (c, r)))
# Row/column conversion to h3 index; given a target H3 resolution, window transformation and pyproj.Transformer
rc2h3 = lambda r, c, res, window_transformation, transformer: h3.geo_to_h3(*rc2lonlat(r, c, window_transformation, transformer)[::-1], res)