Create a water mask in EPSG:4326 using `esa_world_cover_2021` imagery

create-water-mask.py

# /// script
# requires-python = ">=3.12"
# dependencies = [
#     "tile-mate",
#     "tyro",
# ]
# ///
"""Create a water mask in EPSG:4326 using `esa_world_cover_2021` imagery.

Examples
--------
uv run --script create-water-mask.py --output water_mask.tif -120.9 34.85 -120.25 35.15

"""
from pathlib import Path

import rasterio as rio
import tile_mate
import tyro


def download_water_mask(
    bounds: tuple[float, float, float, float], /, output: Path
) -> None:
    """Download a water mask for the given DISP dataset.

    Retrieves a water mask corresponding to the provided DISP dataset and saves it
    in the specified output directory.

    Parameters
    ----------
    bounds : tuple[int, int, int, int]
        (west, south, east, north) in degrees longitude/latitude of requested area.
    output_dir : str | Path
        Directory where the downloaded water mask file will be saved.

    """
    # Create output directory if does not exist
    if output.exists():
        print(f"{output} exists, exiting.")
        return

    print(f"Saving Water Mask: {output}")
    output_dir = output.parent
    output_dir.mkdir(exist_ok=True)

    mask_data, mask_attr = tile_mate.get_raster_from_tiles(
        bounds, tile_shortname="esa_world_cover_2021"
    )

    # Make byte mask
    # class 80 is water
    water_pixels = mask_data == 80
    # 0 was the old nodata
    nodata_pixels = mask_data == 0

    mask_data[:] = 1
    mask_data[water_pixels] = 0
    mask_data[nodata_pixels] = 255
    mask_data = mask_data.astype("byte")
    mask_attr["nodata"] = 255

    with rio.open(output, "w", **mask_attr) as dst:
        dst.write(mask_data)


if __name__ == "__main__":
    tyro.cli(download_water_mask)