Merge pull request #1196 from pelson/repr_html

Add pretty Jupyter repr of Projections

lib/cartopy/crs.py

@@ -156,6 +156,31 @@ def _determine_longitude_bounds(self, central_longitude):
             minlon += epsilon
         return minlon, maxlon
 
+    def _repr_html_(self):
+        import cgi
+        try:
+            # As matplotlib is not a core cartopy dependency, don't error
+            # if it's not available.
+            import matplotlib.pyplot as plt
+        except ImportError:
+            # We can't return an SVG of the CRS, so let Jupyter fall back to
+            # a default repr by returning None.
+            return None
+
+        # Produce a visual repr of the Projection instance.
+        fig, ax = plt.subplots(figsize=(5, 3),
+                               subplot_kw={'projection': self})
+        ax.set_global()
+        ax.coastlines('auto')
+        ax.gridlines()
+        buf = six.StringIO()
+        fig.savefig(buf, format='svg', bbox_inches='tight')
+        plt.close(fig)
+        # "Rewind" the buffer to the start and return it as an svg string.
+        buf.seek(0)
+        svg = buf.read()
+        return '{}<pre>{}</pre>'.format(svg, cgi.escape(repr(self)))
+
     def _as_mpl_axes(self):
         import cartopy.mpl.geoaxes as geoaxes
         return geoaxes.GeoAxes, {'map_projection': self}