Allow destination shape to be specified in reproject()

docs/history.rst

@@ -1,6 +1,11 @@
 History
 =======
 
+Unreleased
+----------
+
+- ENH: Added optional `shape` argument to `rio.reproject` (pull #116)
+
 0.0.26
 ------
 - ENH: Added :func:`rioxarray.show_versions` (issue #106)

rioxarray/rioxarray.py

@@ -203,12 +203,29 @@ def _make_coords(src_data_array, dst_affine, dst_width, dst_height, dst_crs):
     return add_xy_grid_meta(new_coords)
 
 
-def _make_dst_affine(src_data_array, src_crs, dst_crs, dst_resolution=None):
+def _make_dst_affine(
+    src_data_array, src_crs, dst_crs, dst_resolution=None, dst_shape=None
+):
     """Determine the affine of the new projected `xarray.DataArray`"""
     src_bounds = src_data_array.rio.bounds()
     src_width, src_height = src_data_array.rio.shape
+    dst_height, dst_width = dst_shape if dst_shape is not None else (None, None)
+    resolution_or_width_height = {
+        k: v
+        for k, v in [
+            ("resolution", dst_resolution),
+            ("dst_height", dst_height),
+            ("dst_width", dst_width),
+        ]
+        if v is not None
+    }
     dst_affine, dst_width, dst_height = rasterio.warp.calculate_default_transform(
-        src_crs, dst_crs, src_width, src_height, *src_bounds, resolution=dst_resolution
+        src_crs,
+        dst_crs,
+        src_width,
+        src_height,
+        *src_bounds,
+        **resolution_or_width_height,
     )
     return dst_affine, dst_width, dst_height
 
@@ -851,6 +868,7 @@ def reproject(
         self,
         dst_crs,
         resolution=None,
+        shape=None,
         dst_affine_width_height=None,
         resampling=Resampling.nearest,
     ):
@@ -864,13 +882,18 @@ def reproject(
             a 'crs' attribute to be set containing a valid CRS.
             If using a WKT (e.g. from spatiareference.org), make sure it is an OGC WKT.
 
+        .. versionadded:: 0.0.27 shape
+
         Parameters
         ----------
         dst_crs: str
             OGC WKT string or Proj.4 string.
         resolution: float or tuple(float, float), optional
             Size of a destination pixel in destination projection units
             (e.g. degrees or metres).
+        shape: tuple(int, int), optional
+            Shape of the destination in pixels (dst_height, dst_width). Cannot be used
+            together with resolution.
         dst_affine_width_height: tuple(dst_affine, dst_width, dst_height), optional
             Tuple with the destination affine, width, and height.
         resampling: Resampling method, optional
@@ -882,6 +905,8 @@ def reproject(
         :class:`xarray.DataArray`: A reprojected DataArray.
 
         """
+        if resolution is not None and shape is not None:
+            raise RioXarrayError("resolution and shape cannot be used together.")
         if self.crs is None:
             raise MissingCRS(
                 "CRS not found. Please set the CRS with 'set_crs()' or 'write_crs()'."
@@ -892,7 +917,7 @@ def reproject(
             dst_affine, dst_width, dst_height = dst_affine_width_height
         else:
             dst_affine, dst_width, dst_height = _make_dst_affine(
-                self._obj, self.crs, dst_crs, resolution
+                self._obj, self.crs, dst_crs, resolution, shape
             )
         extra_dim = self._check_dimensions()
         if extra_dim:
@@ -1385,6 +1410,7 @@ def reproject(
         self,
         dst_crs,
         resolution=None,
+        shape=None,
         dst_affine_width_height=None,
         resampling=Resampling.nearest,
     ):
@@ -1396,6 +1422,7 @@ def reproject(
             a 'crs' attribute to be set containing a valid CRS.
             If using a WKT (e.g. from spatiareference.org), make sure it is an OGC WKT.
 
+        .. versionadded:: 0.0.27 shape
 
         Parameters
         ----------
@@ -1404,6 +1431,9 @@ def reproject(
         resolution: float or tuple(float, float), optional
             Size of a destination pixel in destination projection units
             (e.g. degrees or metres).
+        shape: tuple(int, int), optional
+            Shape of the destination in pixels (dst_height, dst_width). Cannot be used
+            together with resolution.
         dst_affine_width_height: tuple(dst_affine, dst_width, dst_height), optional
             Tuple with the destination affine, width, and height.
         resampling: Resampling method, optional
@@ -1423,6 +1453,7 @@ def reproject(
                 .rio.reproject(
                     dst_crs,
                     resolution=resolution,
+                    shape=shape,
                     dst_affine_width_height=dst_affine_width_height,
                     resampling=resampling,
                 )

setup.py

@@ -35,7 +35,7 @@ def get_version():
         "nbsphinx",
         "sphinx_rtd_theme",
         "black",
-        "flake8",
+        "flake8==3.7",
         "pylint",
         "isort",
         "pre-commit",

test/integration/test_integration_rioxarray.py

@@ -348,6 +348,23 @@ def test_transform_bounds():
         )
 
 
+def test_reproject_with_shape(modis_reproject):
+    new_shape = (9, 10)
+    mask_args = (
+        dict(masked=False)
+        if "open_rasterio" in str(modis_reproject["open"])
+        else dict(mask_and_scale=False)
+    )
+    with modis_reproject["open"](modis_reproject["input"], **mask_args) as mda:
+        mds_repr = mda.rio.reproject(modis_reproject["to_proj"], shape=new_shape)
+        # test
+        if hasattr(mds_repr, "variables"):
+            for var in mds_repr.rio.vars:
+                assert mds_repr[var].shape == new_shape
+        else:
+            assert mds_repr.shape == new_shape
+
+
 def test_reproject(modis_reproject):
     mask_args = (
         dict(masked=False)
@@ -1256,6 +1273,17 @@ def test_reproject_missing_crs():
         test_da.rio.reproject(4326)
 
 
+def test_reproject_resolution_and_shape():
+    test_da = xarray.DataArray(
+        numpy.zeros((5, 5)),
+        dims=("y", "x"),
+        coords={"y": numpy.arange(1, 6), "x": numpy.arange(2, 7)},
+        attrs={"crs": "+init=epsg:3857"},
+    )
+    with pytest.raises(RioXarrayError):
+        test_da.rio.reproject(4326, resolution=1, shape=(1, 1))
+
+
 class CustomCRS(object):
     @property
     def wkt(self):