Implemented IGH Oceanic View

docs/make_projection.py

@@ -41,6 +41,25 @@ def plate_carree_plot():
         ax.gridlines()
 
 
+def igh_plot():
+    import matplotlib.pyplot as plt
+    import cartopy.crs as ccrs
+
+    fig = plt.figure(figsize=(6.9228, 6))
+
+    ax1 = fig.add_subplot(2, 1, 1,
+                          projection=ccrs.InterruptedGoodeHomolosine(
+                              emphasis='land'))
+    ax1.coastlines(resolution='110m')
+    ax1.gridlines()
+
+    ax2 = fig.add_subplot(2, 1, 2,
+                          projection=ccrs.InterruptedGoodeHomolosine(
+                              central_longitude=-160, emphasis='ocean'))
+    ax2.coastlines(resolution='110m')
+    ax2.gridlines()
+
+
 def utm_plot():
     import matplotlib.pyplot as plt
     import cartopy.crs as ccrs
@@ -59,6 +78,7 @@ def utm_plot():
 
 MULTI_PLOT_CASES = {
     ccrs.PlateCarree: plate_carree_plot,
+    ccrs.InterruptedGoodeHomolosine: igh_plot,
     ccrs.UTM: utm_plot,
 }
 

docs/source/contributors.rst

@@ -41,7 +41,7 @@ the package wouldn't be as rich or diverse as it is today:
  * Sadie Bartholomew
  * Kacper Makuch
  * Stephane Raynaud
-
+ * John Krasting
 
 Thank you!
 

docs/source/reference/projections.rst

@@ -271,10 +271,19 @@ InterruptedGoodeHomolosine
     import matplotlib.pyplot as plt
     import cartopy.crs as ccrs
 
-    plt.figure(figsize=(6.9228, 3))
-    ax = plt.axes(projection=ccrs.InterruptedGoodeHomolosine())
-    ax.coastlines(resolution='110m')
-    ax.gridlines()
+    fig = plt.figure(figsize=(6.9228, 6))
+
+    ax1 = fig.add_subplot(2, 1, 1,
+                          projection=ccrs.InterruptedGoodeHomolosine(
+                              emphasis='land'))
+    ax1.coastlines(resolution='110m')
+    ax1.gridlines()
+
+    ax2 = fig.add_subplot(2, 1, 2,
+                          projection=ccrs.InterruptedGoodeHomolosine(
+                              central_longitude=-160, emphasis='ocean'))
+    ax2.coastlines(resolution='110m')
+    ax2.gridlines()
 
 
 RotatedPole

lib/cartopy/crs.py

@@ -1930,17 +1930,59 @@ def transform_points(self, src_crs, x, y, z=None):
 
 
 class InterruptedGoodeHomolosine(Projection):
-    def __init__(self, central_longitude=0, globe=None):
-        proj4_params = [('proj', 'igh'), ('lon_0', central_longitude)]
-        super().__init__(proj4_params, globe=globe)
+    """
+    Composite equal-area projection empahsizing either land or
+    ocean features.
+
+    Original Reference:
+    Goode, J. P., 1925: The Homolosine Projection: A new device for
+        portraying the Earth's surface entire. Annals of the
+        Association of American Geographers, 15:3, 119-125,
+        DOI: 10.1080/00045602509356949
+
+    A central_longitude value of -160 is recommended for the oceanic view.
+
+    """
+    def __init__(self, central_longitude=0, globe=None, emphasis='land'):
+        """
+        Parameters
+        ----------
+        central_longitude : float, optional
+            The central longitude, by default 0
+        globe : :class:`cartopy.crs.Globe`, optional
+            If omitted, a default Globe object is created, by default None
+        emphasis : str, optional
+            Options 'land' and 'ocean' are available, by default 'land'
+        """
+
+        if emphasis == 'land':
+            proj4_params = [('proj', 'igh'), ('lon_0', central_longitude)]
+            super().__init__(proj4_params, globe=globe)
+
+        elif emphasis == 'ocean':
+            if PROJ4_VERSION < (7, 1, 0):
+                _proj_ver = '.'.join(str(v) for v in PROJ4_VERSION)
+                raise ValueError('The Interrupted Goode Homolosine ocean '
+                                 'projection requires Proj version 7.1.0, '
+                                 'but you are using ' + _proj_ver)
+            proj4_params = [('proj', 'igh_o'), ('lon_0', central_longitude)]
+            super().__init__(proj4_params, globe=globe)
+
+        else:
+            msg = '`emphasis` needs to be either \'land\' or \'ocean\''
+            raise ValueError(msg)
 
         minlon, maxlon = self._determine_longitude_bounds(central_longitude)
         epsilon = 1e-10
 
         # Obtain boundary points
         n = 31
-        top_interrupted_lons = (-40.0,)
-        bottom_interrupted_lons = (80.0, -20.0, -100.0)
+        if emphasis == 'land':
+            top_interrupted_lons = (-40.0,)
+            bottom_interrupted_lons = (80.0, -20.0, -100.0)
+        elif emphasis == 'ocean':
+            top_interrupted_lons = (-90.0, 60.0)
+            bottom_interrupted_lons = (90.0, -60.0)
         lons = np.empty(
             (2 + 2 * len(top_interrupted_lons + bottom_interrupted_lons)) * n +
             1)

lib/cartopy/tests/crs/test_interrupted_goode_homolosine.py

@@ -16,38 +16,61 @@
 from .helpers import check_proj_params
 
 
-def test_default():
-    igh = ccrs.InterruptedGoodeHomolosine()
-    other_args = {'ellps=WGS84', 'lon_0=0'}
-    check_proj_params('igh', igh, other_args)
-
-    assert_almost_equal(np.array(igh.x_limits),
-                        [-20037508.3427892, 20037508.3427892])
-    assert_almost_equal(np.array(igh.y_limits),
-                        [-8683259.7164347, 8683259.7164347])
-
-
-def test_eccentric_globe():
-    globe = ccrs.Globe(semimajor_axis=1000, semiminor_axis=500,
-                       ellipse=None)
-    igh = ccrs.InterruptedGoodeHomolosine(globe=globe)
-    other_args = {'a=1000', 'b=500', 'lon_0=0'}
-    check_proj_params('igh', igh, other_args)
-
-    assert_almost_equal(np.array(igh.x_limits),
-                        [-3141.5926536, 3141.5926536])
-    assert_almost_equal(np.array(igh.y_limits),
-                        [-1361.410035, 1361.410035])
-
-
-@pytest.mark.parametrize('lon', [-10.0, 10.0])
-def test_central_longitude(lon):
-    igh = ccrs.InterruptedGoodeHomolosine(central_longitude=lon)
-    other_args = {'ellps=WGS84', 'lon_0={}'.format(lon)}
-    check_proj_params('igh', igh, other_args)
-
-    assert_almost_equal(np.array(igh.x_limits),
-                        [-20037508.3427892, 20037508.3427892],
-                        decimal=5)
-    assert_almost_equal(np.array(igh.y_limits),
-                        [-8683259.7164347, 8683259.7164347])
+@pytest.mark.parametrize("emphasis", ["land", "ocean"])
+def test_default(emphasis):
+    if emphasis == "ocean" and ccrs.PROJ4_VERSION < (7, 1, 0):
+        pytest.skip()
+    igh = ccrs.InterruptedGoodeHomolosine(emphasis=emphasis)
+    other_args = {"ellps=WGS84", "lon_0=0"}
+    if emphasis == "land":
+        check_proj_params("igh", igh, other_args)
+    elif emphasis == "ocean":
+        check_proj_params("igh_o", igh, other_args)
+    assert_almost_equal(
+        np.array(igh.x_limits), [-20037508.3427892, 20037508.3427892]
+    )
+    assert_almost_equal(
+        np.array(igh.y_limits), [-8683259.7164347, 8683259.7164347]
+    )
+
+
+@pytest.mark.parametrize("emphasis", ["land", "ocean"])
+def test_eccentric_globe(emphasis):
+    if emphasis == "ocean" and ccrs.PROJ4_VERSION < (7, 1, 0):
+        pytest.skip()
+    globe = ccrs.Globe(semimajor_axis=1000, semiminor_axis=500, ellipse=None)
+    igh = ccrs.InterruptedGoodeHomolosine(globe=globe, emphasis=emphasis)
+    other_args = {"a=1000", "b=500", "lon_0=0"}
+    if emphasis == "land":
+        check_proj_params("igh", igh, other_args)
+    elif emphasis == "ocean":
+        check_proj_params("igh_o", igh, other_args)
+
+    assert_almost_equal(np.array(igh.x_limits), [-3141.5926536, 3141.5926536])
+    assert_almost_equal(np.array(igh.y_limits), [-1361.410035, 1361.410035])
+
+
+@pytest.mark.parametrize(
+    ("emphasis", "lon"),
+    [("land", -10.0), ("land", 10.0), ("ocean", -10.0), ("ocean", 10.0)],
+)
+def test_central_longitude(emphasis, lon):
+    if emphasis == "ocean" and ccrs.PROJ4_VERSION < (7, 1, 0):
+        pytest.skip()
+    igh = ccrs.InterruptedGoodeHomolosine(
+        central_longitude=lon, emphasis=emphasis
+    )
+    other_args = {"ellps=WGS84", "lon_0={}".format(lon)}
+    if emphasis == "land":
+        check_proj_params("igh", igh, other_args)
+    elif emphasis == "ocean":
+        check_proj_params("igh_o", igh, other_args)
+
+    assert_almost_equal(
+        np.array(igh.x_limits),
+        [-20037508.3427892, 20037508.3427892],
+        decimal=5,
+    )
+    assert_almost_equal(
+        np.array(igh.y_limits), [-8683259.7164347, 8683259.7164347]
+    )

lib/cartopy/tests/mpl/test_crs.py

@@ -12,6 +12,27 @@
 from cartopy.tests.mpl import ImageTesting
 
 
+@pytest.mark.natural_earth
+@ImageTesting(["igh_land"])
+def test_igh_land():
+    crs = ccrs.InterruptedGoodeHomolosine(emphasis="land")
+    ax = plt.axes(projection=crs)
+    ax.coastlines()
+    ax.gridlines()
+
+
+@pytest.mark.skipif(ccrs.PROJ4_VERSION < (7, 1, 0), reason="Proj is too old.")
+@pytest.mark.natural_earth
+@ImageTesting(["igh_ocean"])
+def test_igh_ocean():
+    crs = ccrs.InterruptedGoodeHomolosine(
+        central_longitude=-160, emphasis="ocean"
+    )
+    ax = plt.axes(projection=crs)
+    ax.coastlines()
+    ax.gridlines()
+
+
 @pytest.mark.natural_earth
 @ImageTesting(['lambert_conformal_south'])
 def test_lambert_south():

lib/cartopy/tests/mpl/test_examples.py

@@ -48,6 +48,8 @@ def test_global_map():
 
 
 contour_image = 'contour_label' if MPL_VERSION < '3.4' else 'contour_label_3.4'
+
+
 @pytest.mark.natural_earth
 @ExampleImageTesting([contour_image], tolerance=0)
 def test_contour_label():

lib/cartopy/tests/mpl/test_gridliner.py

@@ -32,7 +32,7 @@
     ccrs.Robinson,
     ccrs.Sinusoidal,
     ccrs.Stereographic,
-    ccrs.InterruptedGoodeHomolosine,
+    (ccrs.InterruptedGoodeHomolosine, dict(emphasis='land')),
     (ccrs.RotatedPole,
      dict(pole_longitude=180.0,
           pole_latitude=36.0,

lib/cartopy/tests/mpl/test_img_transform.py

@@ -96,7 +96,7 @@ def test_regrid_image():
     # Target grid
     target_nx = 300
     target_ny = 300
-    target_proj = ccrs.InterruptedGoodeHomolosine()
+    target_proj = ccrs.InterruptedGoodeHomolosine(emphasis='land')
     target_x, target_y, target_extent = im_trans.mesh_projection(target_proj,
                                                                  target_nx,
                                                                  target_ny)

lib/cartopy/tests/mpl/test_mpl_integration.py

@@ -212,7 +212,7 @@ def test_multiple_projections():
                    ccrs.SouthPolarStereo(),
                    ccrs.Orthographic(),
                    ccrs.Mollweide(),
-                   ccrs.InterruptedGoodeHomolosine(),
+                   ccrs.InterruptedGoodeHomolosine(emphasis='land'),
                    ccrs.EckertI(),
                    ccrs.EckertII(),
                    ccrs.EckertIII(),
@@ -644,7 +644,7 @@ def test_pcolormesh_goode_wrap():
     X, Y = np.meshgrid(*[np.deg2rad(c) for c in (x, y)])
     Z = np.cos(Y) + 0.375 * np.sin(2. * X)
     Z = Z[:-1, :-1]
-    ax = plt.axes(projection=ccrs.InterruptedGoodeHomolosine())
+    ax = plt.axes(projection=ccrs.InterruptedGoodeHomolosine(emphasis='land'))
     ax.coastlines()
     ax.pcolormesh(x, y, Z, transform=ccrs.PlateCarree())