remove prompt encoder from sam

Author: Rustem Galiullin

segmentation_models_pytorch/decoders/sam/model.py

@@ -3,6 +3,8 @@
 
 import torch
 from segment_anything.modeling import MaskDecoder, TwoWayTransformer, PromptEncoder
+from segment_anything.modeling.prompt_encoder import PositionEmbeddingRandom
+from torch import nn
 from torch.nn import functional as F
 from torch.utils import model_zoo
 
@@ -86,16 +88,12 @@ def __init__(
             out_chans=decoder_channels,
         )
 
+        # this params are used instead of prompt_encoder
         image_embedding_size = image_size // vit_patch_size
-        self.prompt_encoder = PromptEncoder(
-            embed_dim=decoder_channels,
-            image_embedding_size=(image_embedding_size, image_embedding_size),
-            input_image_size=(image_size, image_size),
-            mask_in_chans=16,
-        )
-        self.prompt_encoder.point_embeddings = None
-        self.prompt_encoder.mask_downscaling = None
-        self.not_a_point_embed = None
+        self.embed_dim = decoder_channels
+        self.image_embedding_size = (image_embedding_size, image_embedding_size)
+        self.pe_layer = PositionEmbeddingRandom(decoder_channels // 2)
+        self.no_mask_embed = nn.Embedding(1, decoder_channels)
 
         self.decoder = MaskDecoder(
             num_multimask_outputs=3,
@@ -188,10 +186,11 @@ def forward(self, x):
         img_size = x.shape[-2:]
         x = torch.stack([self.preprocess(img) for img in x])
         features = self.encoder(x)
-        sparse_embeddings, dense_embeddings = self.prompt_encoder(points=None, boxes=None, masks=None)
+        # sparse_embeddings, dense_embeddings = self.prompt_encoder(points=None, boxes=None, masks=None)
+        sparse_embeddings, dense_embeddings = self._get_dummy_promp_encoder_output(x.size(0))
         low_res_masks, iou_predictions = self.decoder(
             image_embeddings=features,
-            image_pe=self.prompt_encoder.get_dense_pe(),
+            image_pe=self._get_dense_pe(),
             sparse_prompt_embeddings=sparse_embeddings,
             dense_prompt_embeddings=dense_embeddings,
             multimask_output=self._decoder_multiclass_output,
@@ -201,3 +200,14 @@ def forward(self, x):
         masks = masks * iou_predictions.view(-1, masks.size(1), 1, 1)
         output = self.segmentation_head(masks)
         return output
+
+    def _get_dummy_promp_encoder_output(self, bs):
+        """Use this dummy output as we're training without prompts."""
+        sparse_embeddings = torch.empty((bs, 0, self.embed_dim), device=self.no_mask_embed.weight.device)
+        dense_embeddings = self.no_mask_embed.weight.reshape(1, -1, 1, 1).expand(
+            bs, -1, self.image_embedding_size[0], self.image_embedding_size[1]
+        )
+        return sparse_embeddings, dense_embeddings
+
+    def _get_dense_pe(self):
+        return self.pe_layer(self.image_embedding_size).unsqueeze(0)

segmentation_models_pytorch/encoders/sam.py

@@ -8,6 +8,11 @@ def __init__(self, name: str, **kwargs):
         super().__init__(**kwargs)
         self._name = name
         self._depth = kwargs["depth"]
+        self._out_chans = kwargs.get("out_chans", 256)
+
+    @property
+    def out_channels(self):
+        return [-1, self._out_chans]
 
 
 sam_vit_encoders = {