adds anchor grid

mmp/a4/anchor_grid.py

@@ -9,4 +9,24 @@ def get_anchor_grid(
     anchor_widths: Sequence[float],
     aspect_ratios: Sequence[float],
 ) -> np.ndarray:
-    raise NotImplementedError()
+    anchor_grid = np.empty(
+        [len(width), len(ratio), num_rows, num_cols, 4], dtype=int)
+    for width_idx, width in enumerate(anchor_widths):
+        for ratio_idx, ratio in enumerate(aspect_ratios):
+            for row in range(num_rows):
+                for col in range(num_cols):
+                    anchor_point = (
+                        col * scale_factor + scale_factor/2, row * scale_factor + scale_factor / 2)
+                    anchor_grid[width_idx, ratio_idx, row, col] = get_box(
+                        width, ratio, anchor_point)
+
+    return anchor_grid
+
+
+def get_box(width: float, ratio: float, anchor_point: tuple[float, float]) -> np.ndarray:
+    box = np.empty(4)
+    box[0] = anchor_point[0] - (width / 2)
+    box[1] = anchor_point[1] - (width * ratio / 2)
+    box[2] = anchor_point[0] + (width / 2)
+    box[3] = anchor_point[1] + (width * ratio / 2)
+    return box