ENH: Add write_transform to store cache in GDAL location (#141)

* ENH: Add write_transform to store cache in GDAL location

* docstring updates

* activate & fix tests

docs/examples/manage_information_loss.ipynb

@@ -13,9 +13,14 @@
     "\n",
     "- [rio.to_raster()](../rioxarray.rst#rioxarray.rioxarray.RasterDataset.to_raster)\n",
     "- [rio.write_crs()](../rioxarray.rst#rioxarray.rioxarray.XRasterBase.write_crs)\n",
+    "- [rio.write_transform()](../rioxarray.rst#rioxarray.rioxarray.XRasterBase.write_transform)\n",
     "- [rio.update_attrs()](../rioxarray.rst#rioxarray.rioxarray.XRasterBase.update_attrs)\n",
     "- [rio.crs](../rioxarray.rst#rioxarray.rioxarray.XRasterBase.crs)\n",
-    "- [rio.nodata](../rioxarray.rst#rioxarray.rioxarray.RasterArray.nodata)"
+    "- [rio.nodata](../rioxarray.rst#rioxarray.rioxarray.RasterArray.nodata)\n",
+    "\n",
+    "Note that `write_transform` is only needed if you are not saving the x,y coordinates. It is for\n",
+    "GDAL to  be able to read in the transform without needing the original coordinates and is useful\n",
+    "if you read in the file with `parse_coordinates=False`."
    ]
   },
   {
@@ -65,7 +70,6 @@
        "  'nodata': 0,\n",
        "  'units': ('DN', 'DN'),\n",
        "  '_FillValue': nan,\n",
-       "  'transform': (3.0, 0.0, 466266.0, 0.0, -3.0, 8084700.0),\n",
        "  'scale_factor': 1.0,\n",
        "  'add_offset': 0.0},\n",
        " CRS.from_epsg(32722),\n",
@@ -129,7 +133,6 @@
        "  'nodata': 0,\n",
        "  'units': ('DN', 'DN'),\n",
        "  '_FillValue': nan,\n",
-       "  'transform': (3.0, 0.0, 466266.0, 0.0, -3.0, 8084700.0),\n",
        "  'scale_factor': 1.0,\n",
        "  'add_offset': 0.0},\n",
        " CRS.from_epsg(32722),\n",
@@ -191,7 +194,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.3"
+   "version": "3.6.10"
   }
  },
  "nbformat": 4,

docs/history.rst

@@ -4,7 +4,7 @@ History
 Latest
 ------
 - BUG: Fix assigning fill value in `rio.pad_box` (pull #140)
-
+- ENH: Add `rio.write_transform` to store cache in GDAL location (issue #129 & #139)
 
 0.0.29
 -------

rioxarray/_io.py

@@ -358,12 +358,6 @@ def _get_rasterio_attrs(riods):
     """
     # Add rasterio attributes
     attrs = _parse_tags(riods.tags(1))
-    # Affine transformation matrix (always available)
-    # This describes coefficients mapping pixel coordinates to CRS
-    # For serialization store as tuple of 6 floats, the last row being
-    # always (0, 0, 1) per definition (see
-    # https://github.com/sgillies/affine)
-    attrs["transform"] = tuple(_rio_transform(riods))[:6]
     if hasattr(riods, "nodata") and riods.nodata is not None:
         # The nodata values for the raster bands
         attrs["_FillValue"] = riods.nodata
@@ -789,6 +783,12 @@ def open_rasterio(
                 result.attrs, result.encoding, "missing_value", name=da_name
             )
 
+    # Affine transformation matrix (always available)
+    # This describes coefficients mapping pixel coordinates to CRS
+    # For serialization store as tuple of 6 floats, the last row being
+    # always (0, 0, 1) per definition (see
+    # https://github.com/sgillies/affine)
+    result.rio.write_transform(riods.transform, inplace=True)
     if hasattr(riods, "crs") and riods.crs:
         result.rio.write_crs(riods.crs, inplace=True)
 

rioxarray/merge.py

@@ -123,7 +123,6 @@ def merge_arrays(
         coords = _get_nonspatial_coords(representative_array)
 
     out_attrs = representative_array.attrs
-    out_attrs["transform"] = tuple(merged_transform)[:6]
     xda = DataArray(
         name=dataarrays[0].name,
         data=merged_data,
@@ -134,6 +133,7 @@ def merge_arrays(
     out_nodata = nodata if nodata is not None else representative_array.rio.nodata
     xda.rio.write_nodata(out_nodata, inplace=True)
     xda.rio.write_crs(representative_array.rio.crs, inplace=True)
+    xda.rio.write_transform(merged_transform, inplace=True)
     return xda