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# Copyright (c) 2022- 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/>. | ||
"""Enhancements related to visualising atmospheric phenomena.""" | ||
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import datetime | ||
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import dask.array as da | ||
import xarray as xr | ||
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def essl_moisture(img, low=1.1, high=1.6) -> None: | ||
r"""Low level moisture by European Severe Storms Laboratory (ESSL). | ||
Expects a mode L image with data corresponding to the ratio of the | ||
calibrated reflectances for the 0.86 µm and 0.906 µm channel. | ||
This composite and its colorisation were developed by ESSL. | ||
Ratio values are scaled from the range ``[low, high]``, which is by default | ||
between 1.1 and 1.6, but might be tuned based on region or sensor, | ||
to ``[0, 1]``. Values outside this range are clipped. Color values | ||
for red, green, and blue are calculated as follows, where ``x`` is the | ||
ratio between the 0.86 µm and 0.905 µm channels: | ||
.. math:: | ||
R = \max(1.375 - 2.67 x, -0.75 + x) \\ | ||
G = 1 - \frac{8x}{7} \\ | ||
B = \max(0.75 - 1.5 x, 0.25 - (x - 0.75)^2) \\ | ||
The value of ``img.data`` is modified in-place. | ||
A color interpretation guide is pending further adjustments to the | ||
parameters for current and future sensors. | ||
Args: | ||
img: XRImage containing the relevant composite | ||
low: optional, low end for scaling, defaults to 1.1 | ||
high: optional, high end for scaling, defaults to 1.6 | ||
""" | ||
ratio = img.data | ||
if _is_fci_test_data(img.data): | ||
# Due to a bug in the FCI pre-launch simulated test data, | ||
# the 0.86 µm channel is too bright. To correct for this, its | ||
# reflectances should be multiplied by 0.8. | ||
ratio *= 0.8 | ||
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with xr.set_options(keep_attrs=True): | ||
ratio = _scale_and_clip(ratio, low, high) | ||
red = _calc_essl_red(ratio) | ||
green = _calc_essl_green(ratio) | ||
blue = _calc_essl_blue(ratio) | ||
data = xr.concat([red, green, blue], dim="bands") | ||
data.attrs["mode"] = "RGB" | ||
data["bands"] = ["R", "G", "B"] | ||
img.data = data | ||
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def _scale_and_clip(ratio, low, high): | ||
"""Scale ratio values to [0, 1] and clip values outside this range.""" | ||
scaled = (ratio - low) / (high - low) | ||
scaled.data = da.clip(scaled.data, 0, 1) | ||
return scaled | ||
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def _calc_essl_red(ratio): | ||
"""Calculate values for red based on scaled and clipped ratio.""" | ||
red_a = 1.375 - 2.67 * ratio | ||
red_b = -0.75 + ratio | ||
red = xr.where(red_a > red_b, red_a, red_b) | ||
red.data = da.clip(red.data, 0, 1) | ||
return red | ||
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def _calc_essl_green(ratio): | ||
"""Calculate values for green based on scaled and clipped ratio.""" | ||
green = 1 - (8/7) * ratio | ||
green.data = da.clip(green.data, 0, 1) | ||
return green | ||
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def _calc_essl_blue(ratio): | ||
"""Calculate values for blue based on scaled and clipped ratio.""" | ||
blue_a = 0.75 - 1.5 * ratio | ||
blue_b = 0.25 - (ratio - 0.75)**2 | ||
blue = xr.where(blue_a > blue_b, blue_a, blue_b) | ||
blue.data = da.clip(blue.data, 0, 1) | ||
return blue | ||
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def _is_fci_test_data(data): | ||
"""Check if we are working with FCI test data.""" | ||
return ("sensor" in data.attrs and | ||
"start_time" in data.attrs and | ||
data.attrs["sensor"] == "fci" and | ||
isinstance(data.attrs["start_time"], datetime.datetime) and | ||
data.attrs["start_time"] < datetime.datetime(2022, 11, 30)) |
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# Copyright (c) 2022- 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/>. | ||
"""Tests for enhancements in enhancements/atmosphere.py.""" | ||
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import datetime | ||
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import dask.array as da | ||
import numpy as np | ||
import xarray as xr | ||
from trollimage.xrimage import XRImage | ||
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def test_essl_moisture(): | ||
"""Test ESSL moisture compositor.""" | ||
from satpy.enhancements.atmosphere import essl_moisture | ||
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ratio = xr.DataArray( | ||
da.linspace(1.0, 1.7, 25, chunks=5).reshape((5, 5)), | ||
dims=("y", "x"), | ||
attrs={"name": "ratio", | ||
"calibration": "reflectance", | ||
"units": "%", | ||
"mode": "L"}) | ||
im = XRImage(ratio) | ||
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essl_moisture(im) | ||
assert im.data.attrs["mode"] == "RGB" | ||
np.testing.assert_array_equal(im.data["bands"], ["R", "G", "B"]) | ||
assert im.data.sel(bands="R")[0, 0] == 1 | ||
np.testing.assert_allclose(im.data.sel(bands="R")[2, 2], 0.04, rtol=1e-4) | ||
np.testing.assert_allclose(im.data.sel(bands="G")[2, 2], 0.42857, rtol=1e-4) | ||
np.testing.assert_allclose(im.data.sel(bands="B")[2, 2], 0.1875, rtol=1e-4) | ||
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# test FCI test data correction | ||
ratio = xr.DataArray( | ||
da.linspace(1.0, 1.7, 25, chunks=5).reshape((5, 5)), | ||
dims=("y", "x"), | ||
attrs={"name": "ratio", | ||
"calibration": "reflectance", | ||
"units": "%", | ||
"mode": "L", | ||
"sensor": "fci", | ||
"start_time": datetime.datetime(1999, 1, 1)}) | ||
im = XRImage(ratio) | ||
essl_moisture(im) | ||
np.testing.assert_allclose(im.data.sel(bands="R")[3, 3], 0.7342, rtol=1e-4) | ||
np.testing.assert_allclose(im.data.sel(bands="G")[3, 3], 0.7257, rtol=1e-4) | ||
np.testing.assert_allclose(im.data.sel(bands="B")[3, 3], 0.39, rtol=1e-4) |
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