pygmt.grdfill: Add new parameter 'inquire' to inquire the bounds of holes

Author: seisman

pygmt/src/grdfill.py

@@ -4,6 +4,7 @@
 
 import warnings
 
+import numpy as np
 import xarray as xr
 from pygmt.clib import Session
 from pygmt.exceptions import GMTInvalidInput
@@ -76,8 +77,9 @@ def grdfill(
     gridfill: str | xr.DataArray | None = None,
     neighborfill: float | bool | None = None,
     splinefill: float | bool | None = None,
+    inquire: bool = False,
     **kwargs,
-) -> xr.DataArray | None:
+) -> xr.DataArray | np.ndarray | None:
     r"""
     Interpolate across holes in a grid.
 
@@ -111,6 +113,9 @@ def grdfill(
     hole : float
         Set the node value used to identify a point as a member of a hole [Default is
         NaN].
+    inquire
+        Output the bounds of each hole. The bounds are 2-D numpy arrays in the form of
+        (west, east, south, north). No grid fill takes place and ``outgrid`` is ignored.
     mode : str
         Specify the hole-filling algorithm to use. Choose from **c** for constant fill
         and append the constant value, **n** for nearest neighbor (and optionally append
@@ -136,42 +141,65 @@ def grdfill(
 
     Example
     -------
+    Fill holes in a bathymetric grid with a constant value of 20.
     >>> import pygmt
     >>> # Load a bathymetric grid with missing data
     >>> earth_relief_holes = pygmt.datasets.load_sample_data(name="earth_relief_holes")
     >>> # Fill the holes with a constant value of 20
     >>> filled_grid = pygmt.grdfill(grid=earth_relief_holes, constantfill=20)
+
+    Inquire the bounds of each hole.
+    >>> pygmt.grdfill(grid=earth_relief_holes, inquire=True)
+    array([[1.83333333, 6.16666667, 3.83333333, 8.16666667],
+           [6.16666667, 7.83333333, 0.5       , 2.5       ]])
     """
+    _fill_pars = "'constantfill'/'gridfill'/'neighborfill'/'splinefill'"
     # TODO(PyGMT>=0.19.0): Remove the deprecated 'mode' parameter.
     if kwargs.get("A") is not None:  # The deprecated 'mode' parameter is given.
-        warnings.warn(
+        msg = (
             "The 'mode' parameter is deprecated since v0.15.0 and will be removed in "
-            "v0.19.0. Use 'constantfill'/'gridfill'/'neighborfill'/'splinefill' "
-            "instead.",
-            FutureWarning,
-            stacklevel=1,
+            f"v0.19.0. Use {_fill_pars} instead."
         )
+        warnings.warn(msg, FutureWarning, stacklevel=1)
     else:
         # Determine the -A option from the fill parameters.
         kwargs["A"] = _parse_fill_mode(constantfill, gridfill, neighborfill, splinefill)
 
-    if kwargs.get("A") is None and kwargs.get("L") is None:
-        msg = "At least parameter 'mode' or 'L' must be specified."
+    if kwargs.get("A") and inquire:
+        msg = f"Parameters {_fill_pars} and 'inquire' are mutually exclusive."
+        raise GMTInvalidInput(msg)
+    if not (kwargs.get("A") or inquire):
+        msg = (
+            f"Need to specify parameter {_fill_pars} for filling holes or 'inquire' "
+            "for inquiring the bounds of each hole."
+        )
         raise GMTInvalidInput(msg)
 
     with Session() as lib:
-        with (
-            lib.virtualfile_in(check_kind="raster", data=grid) as vingrd,
-            lib.virtualfile_in(
-                check_kind="raster", data=gridfill, required_data=False
-            ) as vbggrd,
-            lib.virtualfile_out(kind="grid", fname=outgrid) as voutgrd,
-        ):
-            if gridfill is not None:
-                # Fill by a grid. Append the actual or virtual grid file name.
-                kwargs["A"] = f"g{vbggrd}"
-            kwargs["G"] = voutgrd
-            lib.call_module(
-                module="grdfill", args=build_arg_list(kwargs, infile=vingrd)
-            )
-            return lib.virtualfile_to_raster(vfname=voutgrd, outgrid=outgrid)
+        with lib.virtualfile_in(check_kind="raster", data=grid) as vingrd:
+            if inquire:  # Inquire mode.
+                kwargs["L"] = True
+                with lib.virtualfile_out(kind="dataset") as vouttbl:
+                    lib.call_module(
+                        module="grdfill",
+                        args=build_arg_list(kwargs, infile=vingrd, outfile=vouttbl),
+                    )
+                    return lib.virtualfile_to_dataset(
+                        vfname=vouttbl, output_type="numpy"
+                    )
+
+            # Fill mode.
+            with (
+                lib.virtualfile_in(
+                    check_kind="raster", data=gridfill, required_data=False
+                ) as vbggrd,
+                lib.virtualfile_out(kind="grid", fname=outgrid) as voutgrd,
+            ):
+                if gridfill is not None:
+                    # Fill by a grid. Append the actual or virtual grid file name.
+                    kwargs["A"] = f"g{vbggrd}"
+                kwargs["G"] = voutgrd
+                lib.call_module(
+                    module="grdfill", args=build_arg_list(kwargs, infile=vingrd)
+                )
+                return lib.virtualfile_to_raster(vfname=voutgrd, outgrid=outgrid)

pygmt/tests/test_grdfill.py

@@ -114,14 +114,32 @@ def test_grdfill_gridfill_dataarray(grid):
     npt.assert_array_equal(result[3:6, 3:5], bggrid[3:6, 3:5])
 
 
+def test_grdfill_inquire(grid):
+    """
+    Test grdfill with inquire mode.
+    """
+    bounds = grdfill(grid=grid, inquire=True)
+    assert isinstance(bounds, np.ndarray)
+    assert bounds.shape == (1, 4)
+    npt.assert_allclose(bounds, [[-52.0, -50.0, -21.0, -18.0]])
+
+
 def test_grdfill_required_args(grid):
     """
-    Test that grdfill fails without arguments for `mode` and `L`.
+    Test that grdfill fails without filling parameters or 'inquire'.
     """
     with pytest.raises(GMTInvalidInput):
         grdfill(grid=grid)
 
 
+def test_grdfill_inquire_and_fill(grid):
+    """
+    Grdfill fails if both inquire and fill parameters are given.
+    """
+    with pytest.raises(GMTInvalidInput):
+        grdfill(grid=grid, inquire=True, constantfill=20)
+
+
 # TODO(PyGMT>=0.19.0): Remove this test.
 def test_grdfill_deprecated_mode(grid, expected_grid):
     """