Add attributes to rasterio backend (pydata#1455)

* Add attributes to rasterio backend

Add the 'res', 'tiled', and 'transform' attributes to xarray's rasterio backend.

* Follow flake8 suggestions, update whats-new.rst

* Add period end of line in docs

* Change "tiled" attribute to the actual name, "is_tiled"

Author: gbrener

doc/whats-new.rst

@@ -21,6 +21,10 @@ v0.9.7 (unreleased)
 Enhancements
 ~~~~~~~~~~~~
 
+- More attributes available in :py:attr:`~xarray.Dataset.attrs` dictionary when
+  raster files are opened with :py:func:`~xarray.open_rasterio`.
+  By `Greg Brener <https://github.com/gbrener>`_
+
 Bug fixes
 ~~~~~~~~~
 

xarray/backends/rasterio_.py

@@ -141,7 +141,17 @@ def open_rasterio(filename, chunks=None, cache=None, lock=None):
         # CRS is a dict-like object specific to rasterio
         # We convert it back to a PROJ4 string using rasterio itself
         attrs['crs'] = riods.crs.to_string()
-    # Maybe we'd like to parse other attributes here (for later)
+    if hasattr(riods, 'res'):
+        # (width, height) tuple of pixels in units of CRS
+        attrs['res'] = riods.res
+    if hasattr(riods, 'is_tiled'):
+        # Is the TIF tiled? (bool)
+        # We cast it to an int for netCDF compatibility
+        attrs['is_tiled'] = np.uint8(riods.is_tiled)
+    if hasattr(riods, 'transform'):
+        # Affine transformation matrix (tuple of floats)
+        # Describes coefficients mapping pixel coordinates to CRS
+        attrs['transform'] = tuple(riods.transform)
 
     data = indexing.LazilyIndexedArray(RasterioArrayWrapper(riods))
 

xarray/tests/test_backends.py

@@ -1473,6 +1473,12 @@ def test_serialization_utm(self):
                 assert_allclose(rioda, expected)
                 assert 'crs' in rioda.attrs
                 assert isinstance(rioda.attrs['crs'], basestring)
+                assert 'res' in rioda.attrs
+                assert isinstance(rioda.attrs['res'], tuple)
+                assert 'is_tiled' in rioda.attrs
+                assert isinstance(rioda.attrs['is_tiled'], np.uint8)
+                assert 'transform' in rioda.attrs
+                assert isinstance(rioda.attrs['transform'], tuple)
 
                 # Write it to a netcdf and read again (roundtrip)
                 with create_tmp_file(suffix='.nc') as tmp_nc_file:
@@ -1510,6 +1516,12 @@ def test_serialization_platecarree(self):
                 assert_allclose(rioda, expected)
                 assert 'crs' in rioda.attrs
                 assert isinstance(rioda.attrs['crs'], basestring)
+                assert 'res' in rioda.attrs
+                assert isinstance(rioda.attrs['res'], tuple)
+                assert 'is_tiled' in rioda.attrs
+                assert isinstance(rioda.attrs['is_tiled'], np.uint8)
+                assert 'transform' in rioda.attrs
+                assert isinstance(rioda.attrs['transform'], tuple)
 
                 # Write it to a netcdf and read again (roundtrip)
                 with create_tmp_file(suffix='.nc') as tmp_nc_file: