#!/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/>.
"""Helpers for reading hdf4-based files."""
import logging
import dask.array as da
import numpy as np
import xarray as xr
from pyhdf.SD import SD, SDC, SDS
from satpy.readers.file_handlers import BaseFileHandler
from satpy.utils import get_legacy_chunk_size
LOG = logging.getLogger(__name__)
CHUNK_SIZE = get_legacy_chunk_size()
HTYPE_TO_DTYPE = {
SDC.INT8: np.int8,
SDC.UCHAR: np.uint8,
SDC.CHAR: np.int8,
SDC.INT32: np.int32,
SDC.INT16: np.int16,
SDC.UINT8: np.uint8,
SDC.UINT16: np.uint16,
SDC.UINT32: np.uint32,
SDC.FLOAT32: np.float32,
SDC.FLOAT64: np.float64,
}
[docs]
def from_sds(var, *args, **kwargs):
"""Create a dask array from a SD dataset."""
var.__dict__["dtype"] = np.dtype(HTYPE_TO_DTYPE[var.info()[3]])
shape = var.info()[2]
var.__dict__["shape"] = shape if isinstance(shape, (tuple, list)) else tuple(shape)
return da.from_array(var, *args, **kwargs)
[docs]
class HDF4FileHandler(BaseFileHandler):
"""Base class for common HDF4 operations."""
def __init__(self, filename, filename_info, filetype_info):
"""Open file and collect information."""
super(HDF4FileHandler, self).__init__(filename, filename_info, filetype_info)
self.file_content = {}
file_handle = SD(self.filename, SDC.READ)
self._collect_attrs("", file_handle.attributes())
for k in file_handle.datasets().keys():
self.collect_metadata(k, file_handle.select(k))
del file_handle
[docs]
def _collect_attrs(self, name, attrs):
for key, value in attrs.items():
value = np.squeeze(value)
if issubclass(value.dtype.type, (np.bytes_, np.str_)) and not value.shape:
value = value.item() # convert to scalar
if not isinstance(value, str):
# python 3 - was scalar numpy array of bytes
# otherwise python 2 - scalar numpy array of 'str'
value = value.decode()
self.file_content["{}/attr/{}".format(name, key)] = value
elif not value.shape:
# convert to a scalar
self.file_content["{}/attr/{}".format(name, key)] = value.item()
else:
self.file_content["{}/attr/{}".format(name, key)] = value
[docs]
def _open_xarray_dataset(self, val, chunks=CHUNK_SIZE):
"""Read the band in blocks."""
dask_arr = from_sds(val, chunks=chunks)
attrs = val.attributes()
return xr.DataArray(dask_arr, dims=("y", "x"),
attrs=attrs)
def __getitem__(self, key):
"""Get file content as xarray compatible objects."""
val = self.file_content[key]
if isinstance(val, SDS):
# these datasets are closed and inaccessible when the file is closed, need to reopen
return self._open_xarray_dataset(val)
return val
def __contains__(self, item):
"""Check if item is in file content."""
return item in self.file_content
[docs]
def get(self, item, default=None):
"""Get variable as DataArray or return the default."""
if item in self:
return self[item]
else:
return default