added option to buffer BBox

Author: AleksMat

Diff for: sentinelhub/geometry.py

@@ -239,6 +239,22 @@ def transform(self, crs):
         return BBox((transform_point(self.lower_left, self.crs, new_crs),
                      transform_point(self.upper_right, self.crs, new_crs)), crs=new_crs)
 
+    def buffer(self, buffer):
+        """ Changes both BBox dimensions (width and height) by a percentage of size of each dimension. If number is
+        negative, the size will decrease. Returns a new instance of BBox object.
+
+        :param buffer: A percentage
+        :type buffer: float
+        :return: A new bounding box of buffered size
+        :rtype: BBox
+        """
+        if buffer < -1:
+            raise ValueError('Cannot reduce the bounding box to nothing, buffer must be >= -1.0')
+        ratio = 1 + buffer
+        mid_x, mid_y = self.middle
+        return BBox((mid_x - (mid_x - self.min_x) * ratio, mid_y - (mid_y - self.min_y) * ratio,
+                     mid_x + (self.max_x - mid_x) * ratio, mid_y + (self.max_y - mid_y) * ratio), self.crs)
+
     def get_polygon(self, reverse=False):
         """ Returns a tuple of coordinates of 5 points describing a polygon. Points are listed in clockwise order, first
         point is the same as the last.

Diff for: tests/test_geometry.py

@@ -131,6 +131,12 @@ def test_geometry(self):
                         "Expected type {}, got type {}".format(shapely.geometry.Polygon,
                                                                type(bbox.get_geometry())))
 
+    def test_buffer(self):
+        bbox = BBox([46.07, 13.23, 46.24, 13.57], CRS.WGS84)
+
+        self.assertEqual(bbox, bbox.buffer(0), "Buffer 1 should not change bounding box")
+        self.assertEqual(bbox, bbox.buffer(1).buffer(-0.5), "Twice buffered bounding box should return to original")
+
 
 class TestGeometry(TestSentinelHub):