feat: interpolation

src/bodyparts/head.py

@@ -26,6 +26,7 @@ class Head:
             ],
             dtype=np.float32,
         )
+        self.old_box = np.zeros((4, 1, 2))
 
     def draw(self) -> None:
         """Draw the head on the screen."""
@@ -53,6 +54,10 @@ class Head:
                     self.env.dist_coeff,
                 )
 
+                # interpolation with self.old_box
+                box = (box + self.old_box) / 2
+                self.old_box = box
+
                 a, b, c, d = box.squeeze().astype(int)
                 cv2.line(self.env.frame, a, b, (255, 255, 255), 2)
                 cv2.line(self.env.frame, b, c, (255, 255, 255), 2)