Merge pull request #276 from mraspaud/feature-from_epsg

Create AreaDefinition from epsg codes

pyresample/geometry.py

@@ -1243,6 +1243,25 @@ def y_size(self):
         warnings.warn("'y_size' is deprecated, use 'height' instead.", PendingDeprecationWarning)
         return self.height
 
+    @classmethod
+    def from_epsg(cls, code, resolution):
+        """Create an AreaDefinition object from an epsg code (string or int) and a resolution."""
+        if CRS is None:
+            raise NotImplementedError
+        crs = CRS('EPSG:' + str(code))
+        bounds = crs.area_of_use.bounds
+        proj = Proj(crs)
+        left1, low1 = proj(bounds[0], bounds[1])
+        right1, up1 = proj(bounds[2], bounds[3])
+        left2, up2 = proj(bounds[0], bounds[3])
+        right2, low2 = proj(bounds[2], bounds[1])
+        left = min(left1, left2)
+        right = max(right1, right2)
+        up = max(up1, up2)
+        low = min(low1, low2)
+        area_extent = (left, low, right, up)
+        return create_area_def(crs.name, crs.to_dict(), area_extent=area_extent, resolution=resolution)
+
     @classmethod
     def from_extent(cls, area_id, projection, shape, area_extent, units=None, **kwargs):
         """Create an AreaDefinition object from area_extent and shape.

pyresample/test/test_geometry.py

@@ -1326,6 +1326,21 @@ def test_area_def_geocentric_resolution(self):
         geo_res = area_def.geocentric_resolution()
         np.testing.assert_allclose(298.647232, geo_res)
 
+    def test_from_epsg(self):
+        """Test the from_epsg class method."""
+        from pyresample.geometry import AreaDefinition
+        sweref = AreaDefinition.from_epsg('3006', 2000)
+        assert sweref.name == 'SWEREF99 TM'
+        assert sweref.proj_dict == {'ellps': 'GRS80', 'no_defs': None,
+                                    'proj': 'utm', 'type': 'crs', 'units': 'm',
+                                    'zone': 33}
+        assert sweref.width == 453
+        assert sweref.height == 794
+        import numpy as np
+        np.testing.assert_allclose(sweref.area_extent,
+                                   (181896.3291, 6101648.0705,
+                                    1086312.942376, 7689478.3056))
+
     @unittest.skipIf(CRS is None, "pyproj 2.0+ required")
     def test_area_def_init_projection(self):
         """Test AreaDefinition with different projection definitions."""