# Copyright (c) Meta Platforms, Inc. and affiliates. # All rights reserved. # This source code is licensed under the license found in the # LICENSE file in the root directory of this source tree. import torch from torch import nn from torch.nn import functional as F from typing import Any, Dict, List, Tuple from .image_encoder import ImageEncoderViT from .mask_decoder import MaskDecoder from .prompt_encoder import PromptEncoder from ..utils.amg import calculate_stability_score class Sam(nn.Module): mask_threshold: float = 0.0 image_format: str = "RGB" stability_score_offset: float = 1.0 def __init__( self, image_encoder: ImageEncoderViT, prompt_encoder: PromptEncoder, mask_decoder: MaskDecoder, pixel_mean: List[float] = [123.675, 116.28, 103.53], pixel_std: List[float] = [58.395, 57.12, 57.375], ) -> None: """ SAM predicts object masks from an image and input prompts. Arguments: image_encoder (ImageEncoderViT): The backbone used to encode the image into image embeddings that allow for efficient mask prediction. prompt_encoder (PromptEncoder): Encodes various types of input prompts. mask_decoder (MaskDecoder): Predicts masks from the image embeddings and encoded prompts. pixel_mean (list(float)): Mean values for normalizing pixels in the input image. pixel_std (list(float)): Std values for normalizing pixels in the input image. """ super().__init__() self.image_encoder = image_encoder self.prompt_encoder = prompt_encoder self.mask_decoder = mask_decoder self.register_buffer("pixel_mean", torch.Tensor(pixel_mean).view(-1, 1, 1), False) self.register_buffer("pixel_std", torch.Tensor(pixel_std).view(-1, 1, 1), False) @property def device(self) -> Any: return self.pixel_mean.device @torch.no_grad() def forward_dummy_encoder(self, x): return self.image_encoder(x) @torch.no_grad() def forward( self, batched_input: List[Dict[str, Any]], num_multimask_outputs: int = 1, use_stability_score: bool = False ) -> List[Dict[str, torch.Tensor]]: """ Predicts masks end-to-end from provided images and prompts. If prompts are not known in advance, using SamPredictor is recommended over calling the model directly. Arguments: batched_input (list(dict)): A list over input images, each a dictionary with the following keys. A prompt key can be excluded if it is not present. 'image': The image as a torch tensor in 3xHxW format, already transformed for input to the model. 'original_size': (tuple(int, int)) The original size of the image before transformation, as (H, W). 'point_coords': (torch.Tensor) Batched point prompts for this image, with shape BxNx2. Already transformed to the input frame of the model. 'point_labels': (torch.Tensor) Batched labels for point prompts, with shape BxN. 'boxes': (torch.Tensor) Batched box inputs, with shape Bx4. Already transformed to the input frame of the model. 'mask_inputs': (torch.Tensor) Batched mask inputs to the model, in the form Bx1xHxW. num_multimask_outputs (int): the number of masks to predict when disambiguating masks. Choices: 1, 3, 4. use_stability_score (bool): If true, use stability scores to substitute IoU predictions. Returns: (list(dict)): A list over input images, where each element is as dictionary with the following keys. 'masks': (torch.Tensor) Batched binary mask predictions, with shape BxCxHxW, where B is the number of input prompts, C is determined by multimask_output, and (H, W) is the original size of the image. 'iou_predictions': (torch.Tensor) The model's predictions of mask quality, in shape BxC. 'low_res_logits': (torch.Tensor) Low resolution logits with shape BxCxHxW, where H=W=256. Can be passed as mask input to subsequent iterations of prediction. """ input_images = torch.stack([self.preprocess(x["image"]) for x in batched_input], dim=0) image_embeddings = self.image_encoder(input_images) outputs = [] for image_record, curr_embedding in zip(batched_input, image_embeddings): if "point_coords" in image_record: points = (image_record["point_coords"], image_record["point_labels"]) else: points = None sparse_embeddings, dense_embeddings = self.prompt_encoder( points=points, boxes=image_record.get("boxes", None), masks=image_record.get("mask_inputs", None), ) low_res_masks, iou_predictions = self.mask_decoder( image_embeddings=curr_embedding.unsqueeze(0), image_pe=self.prompt_encoder.get_dense_pe(), sparse_prompt_embeddings=sparse_embeddings, dense_prompt_embeddings=dense_embeddings, num_multimask_outputs=num_multimask_outputs, ) if use_stability_score: iou_predictions = calculate_stability_score( low_res_masks, self.mask_threshold, self.stability_score_offset ) masks = self.postprocess_masks( low_res_masks, input_size=image_record["image"].shape[-2:], original_size=image_record["original_size"], ) masks = masks > self.mask_threshold outputs.append( { "masks": masks, "iou_predictions": iou_predictions, "low_res_logits": low_res_masks, } ) return outputs def postprocess_masks( self, masks: torch.Tensor, input_size: Tuple[int, ...], original_size: Tuple[int, ...], ) -> torch.Tensor: """ Remove padding and upscale masks to the original image size. Arguments: masks (torch.Tensor): Batched masks from the mask_decoder, in BxCxHxW format. input_size (tuple(int, int)): The size of the image input to the model, in (H, W) format. Used to remove padding. original_size (tuple(int, int)): The original size of the image before resizing for input to the model, in (H, W) format. Returns: (torch.Tensor): Batched masks in BxCxHxW format, where (H, W) is given by original_size. """ masks = F.interpolate( masks, (self.image_encoder.img_size, self.image_encoder.img_size), mode="bilinear", align_corners=False, ) masks = masks[..., : input_size[0], : input_size[1]] masks = F.interpolate(masks, original_size, mode="bilinear", align_corners=False) return masks def preprocess(self, x: torch.Tensor) -> torch.Tensor: """Normalize pixel values and pad to a square input.""" # Normalize colors x = (x - self.pixel_mean) / self.pixel_std # Pad h, w = x.shape[-2:] padh = self.image_encoder.img_size - h padw = self.image_encoder.img_size - w x = F.pad(x, (0, padw, 0, padh)) return x