Add vector_buffer (#314)

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
     - `load_ml_model`
     - `unflatten_dimension`
     - `save_ml_model`
+    - `vector_buffer`
     - `vector_to_random_points`
     - `vector_to_regular_points`
 

proposals/vector_buffer.json

@@ -0,0 +1,42 @@
+{
+    "id": "vector_buffer",
+    "summary": "Buffer geometries by distance",
+    "description": "Buffers each input geometry by a given distance, which can either expand (dilate) or a shrink (erode) the geometry. Buffers can be applied to points, lines and polygons, but the results are always polygons. Multi-part types (e.g. `MultiPoint`) are also allowed.",
+    "categories": [
+        "vector"
+    ],
+    "experimental": true,
+    "parameters": [
+        {
+            "name": "geometries",
+            "description": "Geometries to apply the buffer on. Vector properties are preserved for vector data cubes and all GeoJSON Features.\n\nTo maximize interoperability, a nested `GeometryCollection` should be avoided. Furthermore, a `GeometryCollection` composed of a single type of geometries should be avoided in favour of the corresponding multi-part type (e.g. `MultiPolygon`).",
+            "schema": [
+                {
+                    "type": "object",
+                    "subtype": "geojson"
+                },
+                {
+                    "type": "object",
+                    "subtype": "vector-cube"
+                }
+            ]
+        },
+        {
+            "name": "distance",
+            "description": "The distance of the buffer in the unit of the spatial reference system. A positive distance expands the geometries and results in outward buffering (dilation) while a negative distance shrinks the geometries and results in inward buffering (erosion).",
+            "schema": {
+                "type": "number",
+                "not": {
+                    "const": 0
+                }
+            }
+        }
+    ],
+    "returns": {
+        "description": "Returns a vector data cube with the computed new geometries.",
+        "schema": {
+            "type": "object",
+            "subtype": "vector-cube"
+        }
+    }
+}