def _get_raster_tile(self, path: str, *,
upsampling_method: str,
downsampling_method: str,
bounds: Tuple[float, float, float, float] = None,
tile_size: Tuple[int, int] = (256, 256),
preserve_values: bool = False) -> np.ma.MaskedArray:
"""Load a raster dataset from a file through rasterio.
Heavily inspired by mapbox/rio-tiler
"""
import rasterio
from rasterio import transform, windows, warp
from rasterio.vrt import WarpedVRT
from affine import Affine
dst_bounds: Tuple[float, float, float, float]
if preserve_values:
upsampling_enum = downsampling_enum = self._get_resampling_enum('nearest')
else:
upsampling_enum = self._get_resampling_enum(upsampling_method)
downsampling_enum = self._get_resampling_enum(downsampling_method)
with contextlib.ExitStack() as es:
es.enter_context(rasterio.Env(**self._RIO_ENV_KEYS))
try:
with trace('open_dataset'):
src = es.enter_context(rasterio.open(path))
except OSError:
raise IOError('error while reading file {}'.format(path))
# compute suggested resolution and bounds in target CRS
dst_transform, _, _ = self._calculate_default_transform(
src.crs, self._TARGET_CRS, src.width, src.height, *src.bounds
)
dst_res = (abs(dst_transform.a), abs(dst_transform.e))
dst_bounds = warp.transform_bounds(src.crs, self._TARGET_CRS, *src.bounds)
if bounds is None:
bounds = dst_bounds
# pad tile bounds to prevent interpolation artefacts
num_pad_pixels = 2
# compute tile VRT shape and transform
dst_width = max(1, round((bounds[2] - bounds[0]) / dst_res[0]))
dst_height = max(1, round((bounds[3] - bounds[1]) / dst_res[1]))
vrt_transform = (
transform.from_bounds(*bounds, width=dst_width, height=dst_height)
* Affine.translation(-num_pad_pixels, -num_pad_pixels)
)
vrt_height, vrt_width = dst_height + 2 * num_pad_pixels, dst_width + 2 * num_pad_pixels
# remove padding in output
out_window = windows.Window(
col_off=num_pad_pixels, row_off=num_pad_pixels, width=dst_width, height=dst_height
)
# construct VRT
vrt = es.enter_context(
WarpedVRT(
src, crs=self._TARGET_CRS, resampling=upsampling_enum, add_alpha=True,
transform=vrt_transform, width=vrt_width, height=vrt_height
)
)
# prevent loads of very sparse data
out_window_bounds = windows.bounds(out_window, vrt_transform)
cover_ratio = (
(dst_bounds[2] - dst_bounds[0]) / (out_window_bounds[2] - out_window_bounds[0])
* (dst_bounds[3] - dst_bounds[1]) / (out_window_bounds[3] - out_window_bounds[1])
)
if cover_ratio < 0.01:
raise exceptions.TileOutOfBoundsError('dataset covers less than 1% of tile')
# determine whether we are upsampling or downsampling
pixel_ratio = min(out_window.width / tile_size[1], out_window.height / tile_size[0])
if pixel_ratio < 1:
resampling_enum = upsampling_enum
else:
resampling_enum = downsampling_enum
# read data
with warnings.catch_warnings(), trace('read_from_vrt'):
warnings.filterwarnings('ignore', message='invalid value encountered.*')
tile_data = vrt.read(
1, resampling=resampling_enum, window=out_window, out_shape=tile_size
)
# read alpha mask
mask_idx = src.count + 1
mask = vrt.read(mask_idx, window=out_window, out_shape=tile_size) == 0
if src.nodata is not None:
mask |= tile_data == src.nodata
return np.ma.masked_array(tile_data, mask=mask)
def get_raster_tile(
path: str,
*,
reprojection_method: str = "nearest",
resampling_method: str = "nearest",
tile_bounds: Tuple[float, float, float, float] = None,
tile_size: Tuple[int, int] = (256, 256),
preserve_values: bool = False,
target_crs: str = 'epsg:3857',
rio_env_options: Dict[str, Any] = None) -> np.ma.MaskedArray:
"""Load a raster dataset from a file through rasterio.
Heavily inspired by mapbox/rio-tiler
"""
import rasterio
from rasterio import transform, windows, warp
from rasterio.vrt import WarpedVRT
from affine import Affine
dst_bounds: Tuple[float, float, float, float]
if rio_env_options is None:
rio_env_options = {}
if preserve_values:
reproject_enum = resampling_enum = get_resampling_enum('nearest')
else:
reproject_enum = get_resampling_enum(reprojection_method)
resampling_enum = get_resampling_enum(resampling_method)
with contextlib.ExitStack() as es:
es.enter_context(rasterio.Env(**rio_env_options))
try:
with trace('open_dataset'):
src = es.enter_context(rasterio.open(path))
except OSError:
raise IOError('error while reading file {}'.format(path))
# compute buonds in target CRS
dst_bounds = warp.transform_bounds(src.crs, target_crs, *src.bounds)
if tile_bounds is None:
tile_bounds = dst_bounds
# prevent loads of very sparse data
cover_ratio = ((dst_bounds[2] - dst_bounds[0]) /
(tile_bounds[2] - tile_bounds[0]) *
(dst_bounds[3] - dst_bounds[1]) /
(tile_bounds[3] - tile_bounds[1]))
if cover_ratio < 0.01:
raise exceptions.TileOutOfBoundsError(
'dataset covers less than 1% of tile')
# compute suggested resolution in target CRS
dst_transform, _, _ = warp.calculate_default_transform(
src.crs, target_crs, src.width, src.height, *src.bounds)
dst_res = (abs(dst_transform.a), abs(dst_transform.e))
# in some cases (e.g. at extreme latitudes), the default transform
# suggests very coarse resolutions - in this case, fall back to native tile res
tile_transform = transform.from_bounds(*tile_bounds, *tile_size)
tile_res = (abs(tile_transform.a), abs(tile_transform.e))
if tile_res[0] < dst_res[0] or tile_res[1] < dst_res[1]:
dst_res = tile_res
resampling_enum = get_resampling_enum('nearest')
# pad tile bounds to prevent interpolation artefacts
num_pad_pixels = 2
# compute tile VRT shape and transform
dst_width = max(1, round(
(tile_bounds[2] - tile_bounds[0]) / dst_res[0]))
dst_height = max(1,
round((tile_bounds[3] - tile_bounds[1]) / dst_res[1]))
vrt_transform = (transform.from_bounds(
*tile_bounds, width=dst_width, height=dst_height) *
Affine.translation(-num_pad_pixels, -num_pad_pixels))
vrt_height, vrt_width = dst_height + 2 * num_pad_pixels, dst_width + 2 * num_pad_pixels
# remove padding in output
out_window = windows.Window(col_off=num_pad_pixels,
row_off=num_pad_pixels,
width=dst_width,
height=dst_height)
# construct VRT
vrt = es.enter_context(
WarpedVRT(src,
crs=target_crs,
resampling=reproject_enum,
transform=vrt_transform,
width=vrt_width,
height=vrt_height,
add_alpha=not has_alpha_band(src)))
# read data
with warnings.catch_warnings(), trace('read_from_vrt'):
warnings.filterwarnings('ignore',
message='invalid value encountered.*')
tile_data = vrt.read(1,
resampling=resampling_enum,
window=out_window,
out_shape=tile_size)
# assemble alpha mask
mask_idx = vrt.count
mask = vrt.read(mask_idx, window=out_window,
out_shape=tile_size) == 0
if src.nodata is not None:
mask |= tile_data == src.nodata
return np.ma.masked_array(tile_data, mask=mask)