[New Feature] Support SAM 2.1 (#59)

* support sam 2.1

* refine config path and ckpt path

* update README

sam2/modeling/backbones/hieradet.py

@@ -4,12 +4,14 @@
 # This source code is licensed under the license found in the
 # LICENSE file in the root directory of this source tree.
 
+import logging
 from functools import partial
 from typing import List, Tuple, Union
 
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
+from iopath.common.file_io import g_pathmgr
 
 from sam2.modeling.backbones.utils import (
     PatchEmbed,
@@ -193,6 +195,7 @@ class Hiera(nn.Module):
             16,
             20,
         ),
+        weights_path=None,
         return_interm_layers=True,  # return feats from every stage
     ):
         super().__init__()
@@ -262,6 +265,11 @@ class Hiera(nn.Module):
             else [self.blocks[-1].dim_out]
         )
 
+        if weights_path is not None:
+            with g_pathmgr.open(weights_path, "rb") as f:
+                chkpt = torch.load(f, map_location="cpu")
+            logging.info("loading Hiera", self.load_state_dict(chkpt, strict=False))
+
     def _get_pos_embed(self, hw: Tuple[int, int]) -> torch.Tensor:
         h, w = hw
         window_embed = self.pos_embed_window
@@ -289,3 +297,21 @@ class Hiera(nn.Module):
                 outputs.append(feats)
 
         return outputs
+
+    def get_layer_id(self, layer_name):
+        # https://github.com/microsoft/unilm/blob/master/beit/optim_factory.py#L33
+        num_layers = self.get_num_layers()
+
+        if layer_name.find("rel_pos") != -1:
+            return num_layers + 1
+        elif layer_name.find("pos_embed") != -1:
+            return 0
+        elif layer_name.find("patch_embed") != -1:
+            return 0
+        elif layer_name.find("blocks") != -1:
+            return int(layer_name.split("blocks")[1].split(".")[1]) + 1
+        else:
+            return num_layers + 1
+
+    def get_num_layers(self) -> int:
+        return len(self.blocks)

sam2/modeling/backbones/image_encoder.py

@@ -71,6 +71,7 @@ class FpnNeck(nn.Module):
         self.position_encoding = position_encoding
         self.convs = nn.ModuleList()
         self.backbone_channel_list = backbone_channel_list
+        self.d_model = d_model
         for dim in backbone_channel_list:
             current = nn.Sequential()
             current.add_module(