image-footprint.py

import rasterio
from rasterio import Affine as A
from rasterio.warp import transform_geom


def image_boundary(filename, scale=1, tolerance=0.005):
    # open source data
    src = rasterio.open(filename)

    # generate datamask
    arr = src.read(
        1, out_shape=(int(src.shape[0] / scale), int(src.shape[1] / scale))
    )
    arr[numpy.where(arr != 0)] = 1

    transform = src.transform * A.scale(scale)

    for geom, val in rasterio.features.shapes(arr, transform=transform):
        geometry = shape(
            transform_geom(src.crs, "EPSG:4326", geom, precision=3)
        )

        if val == 1:
            geometry = geometry.simplify(tolerance, preserve_topology=True)
            return mapping(geometry)