#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017-2019 Satpy developers
#
# This file is part of satpy.
#
# satpy is free software: you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# satpy is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# satpy. If not, see <http://www.gnu.org/licenses/>.
"""Reader for generic image (e.g. gif, png, jpg, tif, geotiff, ...).
Returns a dataset without calibration. Includes coordinates if
available in the file (eg. geotiff).
If nodata values are present (and rasterio is able to read them), it
will be preserved as attribute ``_FillValue`` in the returned dataset.
In case that nodata values should be used to mask pixels (that have
equal values) with np.nan, it has to be enabled in the reader yaml
file (key ``nodata_handling`` per dataset with value ``"nan_mask"``).
"""
import logging
import dask.array as da
import numpy as np
import rasterio
import xarray as xr
from pyresample import utils
from satpy.readers.file_handlers import BaseFileHandler
from satpy.utils import get_legacy_chunk_size
CHUNK_SIZE = get_legacy_chunk_size()
BANDS = {1: ["L"],
2: ["L", "A"],
3: ["R", "G", "B"],
4: ["R", "G", "B", "A"]}
NODATA_HANDLING_FILLVALUE = "fill_value"
NODATA_HANDLING_NANMASK = "nan_mask"
logger = logging.getLogger(__name__)
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class GenericImageFileHandler(BaseFileHandler):
"""Handle reading of generic image files."""
def __init__(self, filename, filename_info, filetype_info):
"""Initialize filehandler."""
super(GenericImageFileHandler, self).__init__(
filename, filename_info, filetype_info)
self.finfo = filename_info
try:
self.finfo["end_time"] = self.finfo["start_time"]
except KeyError:
pass
self.finfo["filename"] = self.filename
self.file_content = {}
self.area = None
self.dataset_name = None
self.read()
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def read(self):
"""Read the image."""
dataset = rasterio.open(self.finfo["filename"])
# Create area definition
if hasattr(dataset, "crs") and dataset.crs is not None:
self.area = utils.get_area_def_from_raster(dataset)
data = xr.open_dataset(self.finfo["filename"], engine="rasterio",
chunks={"band": 1, "y": CHUNK_SIZE, "x": CHUNK_SIZE}, mask_and_scale=False)["band_data"]
if hasattr(dataset, "nodatavals"):
# The nodata values for the raster bands
# copied from https://github.com/pydata/xarray/blob/v2023.03.0/xarray/backends/rasterio_.py#L322-L326
nodatavals = tuple(
np.nan if nodataval is None else nodataval for nodataval in dataset.nodatavals
)
data.attrs["nodatavals"] = nodatavals
attrs = data.attrs.copy()
# Rename to Satpy convention
data = data.rename({"band": "bands"})
# Rename bands to [R, G, B, A], or a subset of those
data["bands"] = BANDS[data.bands.size]
data.attrs = attrs
self.dataset_name = "image"
self.file_content[self.dataset_name] = data
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def get_area_def(self, dsid):
"""Get area definition of the image."""
if self.area is None:
raise NotImplementedError("No CRS information available from image")
return self.area
@property
def start_time(self):
"""Return start time."""
return self.finfo["start_time"]
@property
def end_time(self):
"""Return end time."""
return self.finfo["end_time"]
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def get_dataset(self, key, info):
"""Get a dataset from the file."""
ds_name = self.dataset_name if self.dataset_name else key["name"]
logger.debug("Reading '%s.'", ds_name)
data = self.file_content[ds_name]
# Mask data if necessary
try:
data = _mask_image_data(data, info)
except ValueError as err:
logger.warning(err)
data.attrs.update(key.to_dict())
data.attrs.update(info)
return data
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def _mask_image_data(data, info):
"""Mask image data if necessary.
Masking is done if alpha channel is present or
dataset 'nodata_handling' is set to 'nan_mask'.
In the latter case even integer data is converted
to float32 and masked with np.nan.
"""
if data.bands.size in (2, 4):
if not np.issubdtype(data.dtype, np.integer):
raise ValueError("Only integer datatypes can be used as a mask.")
mask = data.data[-1, :, :] == np.iinfo(data.dtype).min
data = data.astype(np.float64)
masked_data = da.stack([da.where(mask, np.nan, data.data[i, :, :])
for i in range(data.shape[0])])
data.data = masked_data
data = data.sel(bands=BANDS[data.bands.size - 1])
elif hasattr(data, "nodatavals") and data.nodatavals:
data = _handle_nodatavals(data, info.get("nodata_handling", NODATA_HANDLING_FILLVALUE))
return data
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def _handle_nodatavals(data, nodata_handling):
"""Mask data with np.nan or only set 'attr_FillValue'."""
if nodata_handling == NODATA_HANDLING_NANMASK:
# data converted to float and masked with np.nan
data = data.astype(np.float32)
masked_data = da.stack([da.where(data.data[i, :, :] == nodataval, np.nan, data.data[i, :, :])
for i, nodataval in enumerate(data.nodatavals)])
data.data = masked_data
data.attrs["_FillValue"] = np.nan
elif nodata_handling == NODATA_HANDLING_FILLVALUE:
# keep data as it is but set _FillValue attribute to provided
# nodatavalue (first one as it has to be the same for all bands at least
# in GeoTiff, see GDAL gtiff driver documentation)
fill_value = data.nodatavals[0]
if np.issubdtype(data.dtype, np.integer):
fill_value = int(fill_value)
data.attrs["_FillValue"] = fill_value
return data