Add tests for reading GMT datasets and grids

pygmt/tests/test_clib_read_data.py

@@ -0,0 +1,223 @@
+"""
+Test the Session.read_data method.
+"""
+
+import ctypes as ctp
+from pathlib import Path
+
+import numpy as np
+from pygmt.clib import Session
+from pygmt.datatypes import _GMT_DATASET, _GMT_GRID, _GMT_IMAGE
+from pygmt.helpers import GMTTempFile
+
+
+def test_clib_read_data_dataset():
+    """
+    Test the Session.read_data method for datasets.
+
+    The test is adapted from the doctest in the _GMT_DATASET class.
+    """
+    with GMTTempFile(suffix=".txt") as tmpfile:
+        # Prepare the sample data file
+        with Path(tmpfile.name).open(mode="w", encoding="utf-8") as fp:
+            print("# x y z name", file=fp)
+            print(">", file=fp)
+            print("1.0 2.0 3.0 TEXT1 TEXT23", file=fp)
+            print("4.0 5.0 6.0 TEXT4 TEXT567", file=fp)
+            print(">", file=fp)
+            print("7.0 8.0 9.0 TEXT8 TEXT90", file=fp)
+            print("10.0 11.0 12.0 TEXT123 TEXT456789", file=fp)
+
+        with Session() as lib:
+            data_ptr = lib.read_data(
+                "GMT_IS_DATASET",
+                "GMT_IS_PLP",
+                "GMT_READ_NORMAL",
+                None,
+                tmpfile.name,
+                None,
+            )
+            ds = ctp.cast(data_ptr, ctp.POINTER(_GMT_DATASET)).contents
+
+            assert ds.n_tables == 1
+            assert ds.n_segments == 2
+            assert ds.n_columns == 3
+
+            tbl = ds.table[0].contents
+            assert tbl.min[: tbl.n_columns] == [1.0, 2.0, 3.0]
+            assert tbl.max[: tbl.n_columns] == [10.0, 11.0, 12.0]
+
+
+def test_clib_read_data_grid():
+    """
+    Test the Session.read_data method for grids.
+
+    The test is adapted from the doctest in the _GMT_GRID class.
+    """
+    with Session() as lib:
+        data_ptr = lib.read_data(
+            "GMT_IS_GRID",
+            "GMT_IS_SURFACE",
+            "GMT_CONTAINER_AND_DATA",
+            None,
+            "@static_earth_relief.nc",
+            None,
+        )
+        grid = ctp.cast(data_ptr, ctp.POINTER(_GMT_GRID)).contents
+        header = grid.header.contents
+        assert header.n_rows == 14
+        assert header.n_columns == 8
+        assert header.n_bands == 1
+        assert header.wesn[:] == [-55.0, -47.0, -24.0, -10.0]
+        assert header.z_min == 190.0
+        assert header.z_max == 981.0
+
+        assert grid.data  # The data is read
+        data = np.reshape(grid.data[: header.mx * header.my], (header.my, header.mx))
+        data = data[
+            header.pad[2] : header.my - header.pad[3],
+            header.pad[0] : header.mx - header.pad[1],
+        ]
+        assert data[3][4] == 250.0
+
+
+def test_clib_read_data_grid_two_steps():
+    """
+    Test the Session.read_data method for grids in two steps, first reading the header
+    and then the data.
+
+    The test is adapted from the doctest in the _GMT_GRID class.
+    """
+    family, geometry = "GMT_IS_GRID", "GMT_IS_SURFACE"
+    infile = "@static_earth_relief.nc"
+    with Session() as lib:
+        # Read the header first
+        data_ptr = lib.read_data(
+            family, geometry, "GMT_CONTAINER_ONLY", None, infile, None
+        )
+        grid = ctp.cast(data_ptr, ctp.POINTER(_GMT_GRID)).contents
+        header = grid.header.contents
+        assert header.n_rows == 14
+        assert header.n_columns == 8
+        assert header.n_bands == 1
+        assert header.wesn[:] == [-55.0, -47.0, -24.0, -10.0]
+        assert header.z_min == 190.0
+        assert header.z_max == 981.0
+
+        assert not grid.data  # The data is not read yet
+
+        # Read the data
+        data_ptr = lib.read_data(
+            family, geometry, "GMT_DATA_ONLY", None, infile, data_ptr
+        )
+        grid = ctp.cast(data_ptr, ctp.POINTER(_GMT_GRID)).contents
+
+        assert grid.data  # The data is read
+        header = grid.header.contents
+        data = np.reshape(grid.data[: header.mx * header.my], (header.my, header.mx))
+        data = data[
+            header.pad[2] : header.my - header.pad[3],
+            header.pad[0] : header.mx - header.pad[1],
+        ]
+        assert data[3][4] == 250.0
+
+
+def test_clib_read_data_image_as_grid():
+    """
+    Test the Session.read_data method for images.
+    """
+    with Session() as lib:
+        data_ptr = lib.read_data(
+            "GMT_IS_GRID",
+            "GMT_IS_SURFACE",
+            "GMT_CONTAINER_AND_DATA",
+            None,
+            "@earth_day_01d_p",
+            None,
+        )
+        image = ctp.cast(data_ptr, ctp.POINTER(_GMT_GRID)).contents
+        header = image.header.contents
+        assert header.n_rows == 180
+        assert header.n_columns == 360
+        assert header.n_bands == 1
+        assert header.wesn[:] == [-180.0, 180.0, -90.0, 90.0]
+
+        assert image.data
+
+
+def test_clib_read_data_image():
+    """
+    Test the Session.read_data method for images.
+    """
+    with Session() as lib:
+        data_ptr = lib.read_data(
+            "GMT_IS_IMAGE",
+            "GMT_IS_SURFACE",
+            "GMT_CONTAINER_AND_DATA",
+            None,
+            "@earth_day_01d_p",
+            None,
+        )
+        image = ctp.cast(data_ptr, ctp.POINTER(_GMT_IMAGE)).contents
+        header = image.header.contents
+        assert header.n_rows == 180
+        assert header.n_columns == 360
+        assert header.n_bands == 3
+        assert header.wesn[:] == [-180.0, 180.0, -90.0, 90.0]
+
+        assert image.data
+
+
+def test_clib_read_data_image_two_steps():
+    """
+    Test the Session.read_data method for images in two steps, first reading the header
+    and then the data.
+    """
+    family, geometry = "GMT_IS_IMAGE", "GMT_IS_SURFACE"
+    infile = "@earth_day_01d_p"
+    with Session() as lib:
+        # Read the header first
+        data_ptr = lib.read_data(
+            family, geometry, "GMT_CONTAINER_ONLY", None, infile, None
+        )
+        image = ctp.cast(data_ptr, ctp.POINTER(_GMT_IMAGE)).contents
+        header = image.header.contents
+        assert header.n_rows == 180
+        assert header.n_columns == 360
+        assert header.n_bands == 3
+        assert header.wesn[:] == [-180.0, 180.0, -90.0, 90.0]
+
+        assert not image.data  # The data is not read yet
+
+        # Read the data
+        data_ptr = lib.read_data(
+            family, geometry, "GMT_DATA_ONLY", None, infile, data_ptr
+        )
+        image = ctp.cast(data_ptr, ctp.POINTER(_GMT_GRID)).contents
+
+        assert image.data is not None  # The data is read
+
+
+def test_clib_read_data_grid_as_image():
+    """
+    Test the Session.read_data method for reading a grid as an image.
+
+    Same as test_clib_read_data_image() but with a grid file.
+    """
+    with Session() as lib:
+        data_ptr = lib.read_data(
+            "GMT_IS_IMAGE",
+            "GMT_IS_SURFACE",
+            "GMT_CONTAINER_AND_DATA",
+            None,
+            "@earth_relief_01d_p",
+            None,
+        )
+        image = ctp.cast(data_ptr, ctp.POINTER(_GMT_IMAGE)).contents
+        header = image.header.contents
+        assert header.n_rows == 180
+        assert header.n_columns == 360
+        assert header.n_bands == 1
+        assert header.wesn[:] == [-179.5, 179.5, -89.5, 89.5]
+
+        assert image.data