Add the possibility to include scale and offset in geotiffs

satpy/tests/writer_tests/test_geotiff.py

@@ -15,8 +15,8 @@
 #
 # 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 the geotiff writer.
-"""
+"""Tests for the geotiff writer."""
+
 import sys
 import numpy as np
 
@@ -48,7 +48,7 @@ def tearDown(self):
             pass
 
     def _get_test_datasets(self):
-        """Helper function to create a single test dataset."""
+        """Create a single test dataset."""
         import xarray as xr
         import dask.array as da
         from datetime import datetime
@@ -142,9 +142,21 @@ def test_tags(self):
             called_tags = save_method.call_args[1]['tags']
             self.assertDictEqual(called_tags, {'test1': 1, 'test2': 2})
 
+    def test_scale_offset(self):
+        """Test tags being added."""
+        from satpy.writers.geotiff import GeoTIFFWriter
+        datasets = self._get_test_datasets()
+        w = GeoTIFFWriter(tags={'test1': 1}, base_dir=self.base_dir)
+        w.info['fill_value'] = 128
+        with mock.patch('satpy.writers.XRImage.save') as save_method:
+            save_method.return_value = None
+            w.save_datasets(datasets, tags={'test2': 2}, compute=False, include_scale_offset=True)
+            called_include = save_method.call_args[1]['include_scale_offset_tags']
+            self.assertTrue(called_include)
+
 
 def suite():
-    """The test suite for this writer's tests."""
+    """Test suite for this writer's tests."""
     loader = unittest.TestLoader()
     mysuite = unittest.TestSuite()
     mysuite.addTest(loader.loadTestsFromTestCase(TestGeoTIFFWriter))

satpy/tests/writer_tests/test_ninjotiff.py

@@ -36,6 +36,10 @@ def __init__(self, data, mode):
         self.data = data
         self.mode = mode
 
+    def get_scaling_from_history(self):
+        """Return dummy scale and offset."""
+        return xr.DataArray(1), xr.DataArray(0)
+
 
 modules = {'pyninjotiff': mock.Mock(),
            'pyninjotiff.ninjotiff': mock.Mock()}

satpy/writers/geotiff.py

@@ -15,9 +15,7 @@
 #
 # You should have received a copy of the GNU General Public License along with
 # satpy.  If not, see <http://www.gnu.org/licenses/>.
-"""GeoTIFF writer objects for creating GeoTIFF files from `Dataset` objects.
-
-"""
+"""GeoTIFF writer objects for creating GeoTIFF files from `Dataset` objects."""
 
 import logging
 import numpy as np
@@ -74,6 +72,7 @@ class GeoTIFFWriter(ImageWriter):
                     "copy_src_overviews",)
 
     def __init__(self, dtype=None, tags=None, **kwargs):
+        """Init the writer."""
         super(GeoTIFFWriter, self).__init__(default_config_filename="writers/geotiff.yaml", **kwargs)
         self.dtype = self.info.get("dtype") if dtype is None else dtype
         self.tags = self.info.get("tags", None) if tags is None else tags
@@ -91,6 +90,7 @@ def __init__(self, dtype=None, tags=None, **kwargs):
 
     @classmethod
     def separate_init_kwargs(cls, kwargs):
+        """Separate the init keyword args."""
         # FUTURE: Don't pass Scene.save_datasets kwargs to init and here
         init_kwargs, kwargs = super(GeoTIFFWriter, cls).separate_init_kwargs(
             kwargs)
@@ -101,7 +101,9 @@ def separate_init_kwargs(cls, kwargs):
         return init_kwargs, kwargs
 
     def save_image(self, img, filename=None, dtype=None, fill_value=None,
-                   compute=True, keep_palette=False, cmap=None, **kwargs):
+                   compute=True, keep_palette=False, cmap=None, tags=None,
+                   include_scale_offset=False,
+                   **kwargs):
         """Save the image to the given ``filename`` in geotiff_ format.
 
         Note for faster output and reduced memory usage the ``rasterio``
@@ -145,6 +147,9 @@ def save_image(self, img, filename=None, dtype=None, fill_value=None,
                 the index range of the palette
                 (ex. `cmap.set_range(0, len(colors))`).
             tags (dict): Extra metadata to store in geotiff.
+            include_scale_offset (bool): Activate inclusion of scale and offset
+                factors in the geotiff to allow retrieving original values from
+                the pixel values. ``False`` by default.
 
         .. _geotiff: http://trac.osgeo.org/geotiff/
 
@@ -181,10 +186,11 @@ def save_image(self, img, filename=None, dtype=None, fill_value=None,
             cmap = create_colormap({'colors': img.palette})
             cmap.set_range(0, len(img.palette) - 1)
 
-        tags = kwargs.get('tags', {})
+        if tags is None:
+            tags = {}
         tags.update(self.tags)
         return img.save(filename, fformat='tif', fill_value=fill_value,
                         dtype=dtype, compute=compute,
                         keep_palette=keep_palette, cmap=cmap,
-                        tags=tags,
+                        tags=tags, include_scale_offset_tags=include_scale_offset,
                         **gdal_options)

satpy/writers/ninjotiff.py

@@ -83,6 +83,7 @@
 
 import pyninjotiff.ninjotiff as nt
 from satpy.writers import ImageWriter
+from trollimage.xrimage import invert_scale_offset
 
 
 logger = logging.getLogger(__name__)
@@ -135,19 +136,15 @@ def save_image(self, img, filename=None, compute=True, **kwargs):  # floating_po
             or "ch_max_measurement_unit" not in kwargs
         ):
             try:
-                history = img.data.attrs["enhancement_history"]
-            except KeyError:
-                logger.warning("Cannot find information on previous scaling for ninjo.")
+                scale, offset = img.get_scaling_from_history()
+                scale, offset = invert_scale_offset(scale, offset)
+            except ValueError as err:
+                logger.warning(str(err))
             else:
-                if len(history) > 1:
-                    raise NotImplementedError(
-                        "Don't know how to process large enhancement_history yet"
-                    )
                 try:
-                    scale = history[0]["scale"]
-                    offset = history[0]["offset"]
-                    dmin = -offset / scale
-                    dmax = (1 - offset) / scale
+                    # Here we know that the data if the image is scaled between 0 and 1
+                    dmin = offset
+                    dmax = scale + offset
                     if dmin > dmax:
                         dmin, dmax = dmax, dmin
                     ch_min_measurement_unit, ch_max_measurement_unit = (

satpy/writers/utils.py

@@ -15,11 +15,11 @@
 #
 # You should have received a copy of the GNU General Public License along with
 # satpy.  If not, see <http://www.gnu.org/licenses/>.
-"""Writer utilities"""
+"""Writer utilities."""
 
 
 def flatten_dict(d, parent_key='', sep='_'):
-    """Flatten a nested dictionary
+    """Flatten a nested dictionary.
 
     Based on https://stackoverflow.com/a/6027615/5703449
     """