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import torch
from torch import nn
from sam2.modeling.sam2_utils import LayerNorm2d, MLP
class MaskDecoder(nn.Module):
def __init__(
self,
*,
transformer_dim: int,
transformer: nn.Module,
num_multimask_outputs: int = 3,
activation: Type[nn.Module] = nn.GELU,
iou_head_depth: int = 3,
iou_head_hidden_dim: int = 256,
use_high_res_features: bool = False,
iou_prediction_use_sigmoid=False,
dynamic_multimask_via_stability=False,
dynamic_multimask_stability_delta=0.05,
dynamic_multimask_stability_thresh=0.98,
pred_obj_scores: bool = False,
pred_obj_scores_mlp: bool = False,
use_multimask_token_for_obj_ptr: bool = False,
) -> None:
super().__init__()
self.transformer_dim = transformer_dim
self.transformer = transformer
self.num_multimask_outputs = num_multimask_outputs
self.iou_token = nn.Embedding(1, transformer_dim)
self.num_mask_tokens = num_multimask_outputs + 1
self.mask_tokens = nn.Embedding(self.num_mask_tokens, transformer_dim)
self.pred_obj_scores = pred_obj_scores
if self.pred_obj_scores:
self.obj_score_token = nn.Embedding(1, transformer_dim)
self.use_multimask_token_for_obj_ptr = use_multimask_token_for_obj_ptr
self.output_upscaling = nn.Sequential(
nn.ConvTranspose2d(
transformer_dim, transformer_dim // 4, kernel_size=2, stride=2
),
LayerNorm2d(transformer_dim // 4),
activation(),
nn.ConvTranspose2d(
transformer_dim // 4, transformer_dim // 8, kernel_size=2, stride=2
),
activation(),
)
self.use_high_res_features = use_high_res_features
if use_high_res_features:
self.conv_s0 = nn.Conv2d(
transformer_dim, transformer_dim // 8, kernel_size=1, stride=1
)
self.conv_s1 = nn.Conv2d(
transformer_dim, transformer_dim // 4, kernel_size=1, stride=1
)
self.output_hypernetworks_mlps = nn.ModuleList(
[
MLP(transformer_dim, transformer_dim, transformer_dim // 8, 3)
for i in range(self.num_mask_tokens)
]
)
self.iou_prediction_head = MLP(
transformer_dim,
iou_head_hidden_dim,
self.num_mask_tokens,
iou_head_depth,
sigmoid_output=iou_prediction_use_sigmoid,
)
if self.pred_obj_scores:
self.pred_obj_score_head = nn.Linear(transformer_dim, 1)
if pred_obj_scores_mlp:
self.pred_obj_score_head = MLP(transformer_dim, transformer_dim, 1, 3)
self.dynamic_multimask_via_stability = dynamic_multimask_via_stability
self.dynamic_multimask_stability_delta = dynamic_multimask_stability_delta
self.dynamic_multimask_stability_thresh = dynamic_multimask_stability_thresh
def forward(
self,
image_embeddings: torch.Tensor,
image_pe: torch.Tensor,
sparse_prompt_embeddings: torch.Tensor,
dense_prompt_embeddings: torch.Tensor,
multimask_output: bool,
repeat_image: bool,
high_res_features: Optional[List[torch.Tensor]] = None,
) -> Tuple[torch.Tensor, torch.Tensor]:
masks, iou_pred, mask_tokens_out, object_score_logits = self.predict_masks(
image_embeddings=image_embeddings,
image_pe=image_pe,
sparse_prompt_embeddings=sparse_prompt_embeddings,
dense_prompt_embeddings=dense_prompt_embeddings,
repeat_image=repeat_image,
high_res_features=high_res_features,
)
if multimask_output:
masks = masks[:, 1:, :, :]
iou_pred = iou_pred[:, 1:]
elif self.dynamic_multimask_via_stability and not self.training:
masks, iou_pred = self._dynamic_multimask_via_stability(masks, iou_pred)
else:
masks = masks[:, 0:1, :, :]
iou_pred = iou_pred[:, 0:1]
if multimask_output and self.use_multimask_token_for_obj_ptr:
sam_tokens_out = mask_tokens_out[:, 1:]
else:
sam_tokens_out = mask_tokens_out[:, 0:1]
return masks, iou_pred, sam_tokens_out, object_score_logits
def predict_masks(
self,
image_embeddings: torch.Tensor,
image_pe: torch.Tensor,
sparse_prompt_embeddings: torch.Tensor,
dense_prompt_embeddings: torch.Tensor,
repeat_image: bool,
high_res_features: Optional[List[torch.Tensor]] = None,
) -> Tuple[torch.Tensor, torch.Tensor]:
s = 0
if self.pred_obj_scores:
output_tokens = torch.cat(
[
self.obj_score_token.weight,
self.iou_token.weight,
self.mask_tokens.weight,
],
dim=0,
)
s = 1
else:
output_tokens = torch.cat(
[self.iou_token.weight, self.mask_tokens.weight], dim=0
)
output_tokens = output_tokens.unsqueeze(0).expand(
sparse_prompt_embeddings.size(0), -1, -1
)
tokens = torch.cat((output_tokens, sparse_prompt_embeddings), dim=1)
if repeat_image:
src = torch.repeat_interleave(image_embeddings, tokens.shape[0], dim=0)
else:
assert image_embeddings.shape[0] == tokens.shape[0]
src = image_embeddings
src = src + dense_prompt_embeddings
assert (
image_pe.size(0) == 1
), "image_pe should have size 1 in batch dim (from `get_dense_pe()`)"
pos_src = torch.repeat_interleave(image_pe, tokens.shape[0], dim=0)
b, c, h, w = src.shape
hs, src = self.transformer(src, pos_src, tokens)
iou_token_out = hs[:, s, :]
mask_tokens_out = hs[:, s + 1 : (s + 1 + self.num_mask_tokens), :]
src = src.transpose(1, 2).view(b, c, h, w)
if not self.use_high_res_features:
upscaled_embedding = self.output_upscaling(src)
else:
dc1, ln1, act1, dc2, act2 = self.output_upscaling
feat_s0, feat_s1 = high_res_features
upscaled_embedding = act1(ln1(dc1(src) + feat_s1))
upscaled_embedding = act2(dc2(upscaled_embedding) + feat_s0)
hyper_in_list: List[torch.Tensor] = []
for i in range(self.num_mask_tokens):
hyper_in_list.append(
self.output_hypernetworks_mlps[i](mask_tokens_out[:, i, :])
)
hyper_in = torch.stack(hyper_in_list, dim=1)
b, c, h, w = upscaled_embedding.shape
masks = (hyper_in @ upscaled_embedding.view(b, c, h * w)).view(b, -1, h, w)
iou_pred = self.iou_prediction_head(iou_token_out)
if self.pred_obj_scores:
assert s == 1
object_score_logits = self.pred_obj_score_head(hs[:, 0, :])
else:
object_score_logits = 10.0 * iou_pred.new_ones(iou_pred.shape[0], 1)
return masks, iou_pred, mask_tokens_out, object_score_logits
def _get_stability_scores(self, mask_logits):
mask_logits = mask_logits.flatten(-2)
stability_delta = self.dynamic_multimask_stability_delta
area_i = torch.sum(mask_logits > stability_delta, dim=-1).float()
area_u = torch.sum(mask_logits > -stability_delta, dim=-1).float()
stability_scores = torch.where(area_u > 0, area_i / area_u, 1.0)
return stability_scores
def _dynamic_multimask_via_stability(self, all_mask_logits, all_iou_scores):
multimask_logits = all_mask_logits[:, 1:, :, :]
multimask_iou_scores = all_iou_scores[:, 1:]
best_scores_inds = torch.argmax(multimask_iou_scores, dim=-1)
batch_inds = torch.arange(
multimask_iou_scores.size(0), device=all_iou_scores.device
)
best_multimask_logits = multimask_logits[batch_inds, best_scores_inds]
best_multimask_logits = best_multimask_logits.unsqueeze(1)
best_multimask_iou_scores = multimask_iou_scores[batch_inds, best_scores_inds]
best_multimask_iou_scores = best_multimask_iou_scores.unsqueeze(1)
singlemask_logits = all_mask_logits[:, 0:1, :, :]
singlemask_iou_scores = all_iou_scores[:, 0:1]
stability_scores = self._get_stability_scores(singlemask_logits)
is_stable = stability_scores >= self.dynamic_multimask_stability_thresh
mask_logits_out = torch.where(
is_stable[..., None, None].expand_as(singlemask_logits),
singlemask_logits,
best_multimask_logits,
)
iou_scores_out = torch.where(
is_stable.expand_as(singlemask_iou_scores),
singlemask_iou_scores,
best_multimask_iou_scores,
)
return mask_logits_out, iou_scores_out
|