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Reference for ultralytics/models/sam/predict.py

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This file is available at https://github.com/ultralytics/ultralytics/blob/main/ultralytics/models/sam/predict.py. If you spot a problem please help fix it by contributing a Pull Request 🛠️. Thank you 🙏!


ultralytics.models.sam.predict.Predictor

Predictor(cfg=DEFAULT_CFG, overrides=None, _callbacks=None)

Bases: BasePredictor

Predictor class for SAM, enabling real-time image segmentation with promptable capabilities.

This class extends BasePredictor and implements the Segment Anything Model (SAM) for advanced image segmentation tasks. It supports various input prompts like points, bounding boxes, and masks for fine-grained control over segmentation results.

Attributes:

NameTypeDescription
argsSimpleNamespace

Configuration arguments for the predictor.

modelModule

The loaded SAM model.

devicedevice

The device (CPU or GPU) on which the model is loaded.

imTensor

The preprocessed input image.

featuresTensor

Extracted image features.

promptsDict

Dictionary to store various types of prompts (e.g., bboxes, points, masks).

segment_allbool

Flag to indicate if full image segmentation should be performed.

meanTensor

Mean values for image normalization.

stdTensor

Standard deviation values for image normalization.

Methods:

NameDescription
preprocess

Prepares input images for model inference.

pre_transform

Performs initial transformations on the input image.

inference

Performs segmentation inference based on input prompts.

prompt_inference

Internal function for prompt-based segmentation inference.

generate

Generates segmentation masks for an entire image.

setup_model

Initializes the SAM model for inference.

get_model

Builds and returns a SAM model.

postprocess

Post-processes model outputs to generate final results.

setup_source

Sets up the data source for inference.

set_image

Sets and preprocesses a single image for inference.

get_im_features

Extracts image features using the SAM image encoder.

set_prompts

Sets prompts for subsequent inference.

reset_image

Resets the current image and its features.

remove_small_regions

Removes small disconnected regions and holes from masks.

Examples:

>>> predictor = Predictor()
>>> predictor.setup_model(model_path="sam_model.pt")
>>> predictor.set_image("image.jpg")
>>> masks, scores, boxes = predictor.generate()
>>> results = predictor.postprocess((masks, scores, boxes), im, orig_img)

Sets up the Predictor object for SAM (Segment Anything Model) and applies any configuration overrides or callbacks provided. Initializes task-specific settings for SAM, such as retina_masks being set to True for optimal results.

Parameters:

NameTypeDescriptionDefault
cfgDict

Configuration dictionary containing default settings.

DEFAULT_CFG
overridesDict | None

Dictionary of values to override default configuration.

None
_callbacksDict | None

Dictionary of callback functions to customize behavior.

None

Examples:

>>> predictor = Predictor(cfg=DEFAULT_CFG)
>>> predictor = Predictor(overrides={"imgsz": 640})
>>> predictor = Predictor(_callbacks={"on_predict_start": custom_callback})
Source code in ultralytics/models/sam/predict.py
def __init__(self, cfg=DEFAULT_CFG, overrides=None, _callbacks=None):
    """
    Initialize the Predictor with configuration, overrides, and callbacks.

    Sets up the Predictor object for SAM (Segment Anything Model) and applies any configuration overrides or
    callbacks provided. Initializes task-specific settings for SAM, such as retina_masks being set to True
    for optimal results.

    Args:
        cfg (Dict): Configuration dictionary containing default settings.
        overrides (Dict | None): Dictionary of values to override default configuration.
        _callbacks (Dict | None): Dictionary of callback functions to customize behavior.

    Examples:
        >>> predictor = Predictor(cfg=DEFAULT_CFG)
        >>> predictor = Predictor(overrides={"imgsz": 640})
        >>> predictor = Predictor(_callbacks={"on_predict_start": custom_callback})
    """
    if overrides is None:
        overrides = {}
    overrides.update(dict(task="segment", mode="predict"))
    super().__init__(cfg, overrides, _callbacks)
    self.args.retina_masks = True
    self.im = None
    self.features = None
    self.prompts = {}
    self.segment_all = False

generate

generate(
    im,
    crop_n_layers=0,
    crop_overlap_ratio=512 / 1500,
    crop_downscale_factor=1,
    point_grids=None,
    points_stride=32,
    points_batch_size=64,
    conf_thres=0.88,
    stability_score_thresh=0.95,
    stability_score_offset=0.95,
    crop_nms_thresh=0.7,
)

Perform image segmentation using the Segment Anything Model (SAM).

This method segments an entire image into constituent parts by leveraging SAM's advanced architecture and real-time performance capabilities. It can optionally work on image crops for finer segmentation.

Parameters:

NameTypeDescriptionDefault
imTensor

Input tensor representing the preprocessed image with shape (N, C, H, W).

required
crop_n_layersint

Number of layers for additional mask predictions on image crops.

0
crop_overlap_ratiofloat

Overlap between crops, scaled down in subsequent layers.

512 / 1500
crop_downscale_factorint

Scaling factor for sampled points-per-side in each layer.

1
point_gridsList[ndarray] | None

Custom grids for point sampling normalized to [0,1].

None
points_strideint

Number of points to sample along each side of the image.

32
points_batch_sizeint

Batch size for the number of points processed simultaneously.

64
conf_thresfloat

Confidence threshold [0,1] for filtering based on mask quality prediction.

0.88
stability_score_threshfloat

Stability threshold [0,1] for mask filtering based on stability.

0.95
stability_score_offsetfloat

Offset value for calculating stability score.

0.95
crop_nms_threshfloat

IoU cutoff for NMS to remove duplicate masks between crops.

0.7

Returns:

TypeDescription
Tuple[Tensor, Tensor, Tensor]

A tuple containing: - pred_masks (torch.Tensor): Segmented masks with shape (N, H, W). - pred_scores (torch.Tensor): Confidence scores for each mask with shape (N,). - pred_bboxes (torch.Tensor): Bounding boxes for each mask with shape (N, 4).

Examples:

>>> predictor = Predictor()
>>> im = torch.rand(1, 3, 1024, 1024)  # Example input image
>>> masks, scores, boxes = predictor.generate(im)
Source code in ultralytics/models/sam/predict.py
def generate(
    self,
    im,
    crop_n_layers=0,
    crop_overlap_ratio=512 / 1500,
    crop_downscale_factor=1,
    point_grids=None,
    points_stride=32,
    points_batch_size=64,
    conf_thres=0.88,
    stability_score_thresh=0.95,
    stability_score_offset=0.95,
    crop_nms_thresh=0.7,
):
    """
    Perform image segmentation using the Segment Anything Model (SAM).

    This method segments an entire image into constituent parts by leveraging SAM's advanced architecture
    and real-time performance capabilities. It can optionally work on image crops for finer segmentation.

    Args:
        im (torch.Tensor): Input tensor representing the preprocessed image with shape (N, C, H, W).
        crop_n_layers (int): Number of layers for additional mask predictions on image crops.
        crop_overlap_ratio (float): Overlap between crops, scaled down in subsequent layers.
        crop_downscale_factor (int): Scaling factor for sampled points-per-side in each layer.
        point_grids (List[np.ndarray] | None): Custom grids for point sampling normalized to [0,1].
        points_stride (int): Number of points to sample along each side of the image.
        points_batch_size (int): Batch size for the number of points processed simultaneously.
        conf_thres (float): Confidence threshold [0,1] for filtering based on mask quality prediction.
        stability_score_thresh (float): Stability threshold [0,1] for mask filtering based on stability.
        stability_score_offset (float): Offset value for calculating stability score.
        crop_nms_thresh (float): IoU cutoff for NMS to remove duplicate masks between crops.

    Returns:
        (Tuple[torch.Tensor, torch.Tensor, torch.Tensor]): A tuple containing:
            - pred_masks (torch.Tensor): Segmented masks with shape (N, H, W).
            - pred_scores (torch.Tensor): Confidence scores for each mask with shape (N,).
            - pred_bboxes (torch.Tensor): Bounding boxes for each mask with shape (N, 4).

    Examples:
        >>> predictor = Predictor()
        >>> im = torch.rand(1, 3, 1024, 1024)  # Example input image
        >>> masks, scores, boxes = predictor.generate(im)
    """
    import torchvision  # scope for faster 'import ultralytics'

    self.segment_all = True
    ih, iw = im.shape[2:]
    crop_regions, layer_idxs = generate_crop_boxes((ih, iw), crop_n_layers, crop_overlap_ratio)
    if point_grids is None:
        point_grids = build_all_layer_point_grids(points_stride, crop_n_layers, crop_downscale_factor)
    pred_masks, pred_scores, pred_bboxes, region_areas = [], [], [], []
    for crop_region, layer_idx in zip(crop_regions, layer_idxs):
        x1, y1, x2, y2 = crop_region
        w, h = x2 - x1, y2 - y1
        area = torch.tensor(w * h, device=im.device)
        points_scale = np.array([[w, h]])  # w, h
        # Crop image and interpolate to input size
        crop_im = F.interpolate(im[..., y1:y2, x1:x2], (ih, iw), mode="bilinear", align_corners=False)
        # (num_points, 2)
        points_for_image = point_grids[layer_idx] * points_scale
        crop_masks, crop_scores, crop_bboxes = [], [], []
        for (points,) in batch_iterator(points_batch_size, points_for_image):
            pred_mask, pred_score = self.prompt_inference(crop_im, points=points, multimask_output=True)
            # Interpolate predicted masks to input size
            pred_mask = F.interpolate(pred_mask[None], (h, w), mode="bilinear", align_corners=False)[0]
            idx = pred_score > conf_thres
            pred_mask, pred_score = pred_mask[idx], pred_score[idx]

            stability_score = calculate_stability_score(
                pred_mask, self.model.mask_threshold, stability_score_offset
            )
            idx = stability_score > stability_score_thresh
            pred_mask, pred_score = pred_mask[idx], pred_score[idx]
            # Bool type is much more memory-efficient.
            pred_mask = pred_mask > self.model.mask_threshold
            # (N, 4)
            pred_bbox = batched_mask_to_box(pred_mask).float()
            keep_mask = ~is_box_near_crop_edge(pred_bbox, crop_region, [0, 0, iw, ih])
            if not torch.all(keep_mask):
                pred_bbox, pred_mask, pred_score = pred_bbox[keep_mask], pred_mask[keep_mask], pred_score[keep_mask]

            crop_masks.append(pred_mask)
            crop_bboxes.append(pred_bbox)
            crop_scores.append(pred_score)

        # Do nms within this crop
        crop_masks = torch.cat(crop_masks)
        crop_bboxes = torch.cat(crop_bboxes)
        crop_scores = torch.cat(crop_scores)
        keep = torchvision.ops.nms(crop_bboxes, crop_scores, self.args.iou)  # NMS
        crop_bboxes = uncrop_boxes_xyxy(crop_bboxes[keep], crop_region)
        crop_masks = uncrop_masks(crop_masks[keep], crop_region, ih, iw)
        crop_scores = crop_scores[keep]

        pred_masks.append(crop_masks)
        pred_bboxes.append(crop_bboxes)
        pred_scores.append(crop_scores)
        region_areas.append(area.expand(len(crop_masks)))

    pred_masks = torch.cat(pred_masks)
    pred_bboxes = torch.cat(pred_bboxes)
    pred_scores = torch.cat(pred_scores)
    region_areas = torch.cat(region_areas)

    # Remove duplicate masks between crops
    if len(crop_regions) > 1:
        scores = 1 / region_areas
        keep = torchvision.ops.nms(pred_bboxes, scores, crop_nms_thresh)
        pred_masks, pred_bboxes, pred_scores = pred_masks[keep], pred_bboxes[keep], pred_scores[keep]

    return pred_masks, pred_scores, pred_bboxes

get_im_features

get_im_features(im)

Extracts image features using the SAM model's image encoder for subsequent mask prediction.

Source code in ultralytics/models/sam/predict.py
def get_im_features(self, im):
    """Extracts image features using the SAM model's image encoder for subsequent mask prediction."""
    assert (
        isinstance(self.imgsz, (tuple, list)) and self.imgsz[0] == self.imgsz[1]
    ), f"SAM models only support square image size, but got {self.imgsz}."
    self.model.set_imgsz(self.imgsz)
    return self.model.image_encoder(im)

get_model

get_model()

Retrieves or builds the Segment Anything Model (SAM) for image segmentation tasks.

Source code in ultralytics/models/sam/predict.py
def get_model(self):
    """Retrieves or builds the Segment Anything Model (SAM) for image segmentation tasks."""
    return build_sam(self.args.model)

inference

inference(
    im,
    bboxes=None,
    points=None,
    labels=None,
    masks=None,
    multimask_output=False,
    *args,
    **kwargs
)

Perform image segmentation inference based on the given input cues, using the currently loaded image.

This method leverages SAM's (Segment Anything Model) architecture consisting of image encoder, prompt encoder, and mask decoder for real-time and promptable segmentation tasks.

Parameters:

NameTypeDescriptionDefault
imTensor

The preprocessed input image in tensor format, with shape (N, C, H, W).

required
bboxesndarray | List | None

Bounding boxes with shape (N, 4), in XYXY format.

None
pointsndarray | List | None

Points indicating object locations with shape (N, 2), in pixels.

None
labelsndarray | List | None

Labels for point prompts, shape (N,). 1 = foreground, 0 = background.

None
masksndarray | None

Low-resolution masks from previous predictions, shape (N, H, W). For SAM H=W=256.

None
multimask_outputbool

Flag to return multiple masks. Helpful for ambiguous prompts.

False
*argsAny

Additional positional arguments.

()
**kwargsAny

Additional keyword arguments.

{}

Returns:

TypeDescription
tuple

Contains the following three elements: - np.ndarray: The output masks in shape (C, H, W), where C is the number of generated masks. - np.ndarray: An array of length C containing quality scores predicted by the model for each mask. - np.ndarray: Low-resolution logits of shape (C, H, W) for subsequent inference, where H=W=256.

Examples:

>>> predictor = Predictor()
>>> predictor.setup_model(model_path="sam_model.pt")
>>> predictor.set_image("image.jpg")
>>> masks, scores, logits = predictor.inference(im, bboxes=[[0, 0, 100, 100]])
Source code in ultralytics/models/sam/predict.py
def inference(self, im, bboxes=None, points=None, labels=None, masks=None, multimask_output=False, *args, **kwargs):
    """
    Perform image segmentation inference based on the given input cues, using the currently loaded image.

    This method leverages SAM's (Segment Anything Model) architecture consisting of image encoder, prompt
    encoder, and mask decoder for real-time and promptable segmentation tasks.

    Args:
        im (torch.Tensor): The preprocessed input image in tensor format, with shape (N, C, H, W).
        bboxes (np.ndarray | List | None): Bounding boxes with shape (N, 4), in XYXY format.
        points (np.ndarray | List | None): Points indicating object locations with shape (N, 2), in pixels.
        labels (np.ndarray | List | None): Labels for point prompts, shape (N,). 1 = foreground, 0 = background.
        masks (np.ndarray | None): Low-resolution masks from previous predictions, shape (N, H, W). For SAM H=W=256.
        multimask_output (bool): Flag to return multiple masks. Helpful for ambiguous prompts.
        *args (Any): Additional positional arguments.
        **kwargs (Any): Additional keyword arguments.

    Returns:
        (tuple): Contains the following three elements:
            - np.ndarray: The output masks in shape (C, H, W), where C is the number of generated masks.
            - np.ndarray: An array of length C containing quality scores predicted by the model for each mask.
            - np.ndarray: Low-resolution logits of shape (C, H, W) for subsequent inference, where H=W=256.

    Examples:
        >>> predictor = Predictor()
        >>> predictor.setup_model(model_path="sam_model.pt")
        >>> predictor.set_image("image.jpg")
        >>> masks, scores, logits = predictor.inference(im, bboxes=[[0, 0, 100, 100]])
    """
    # Override prompts if any stored in self.prompts
    bboxes = self.prompts.pop("bboxes", bboxes)
    points = self.prompts.pop("points", points)
    masks = self.prompts.pop("masks", masks)
    labels = self.prompts.pop("labels", labels)

    if all(i is None for i in [bboxes, points, masks]):
        return self.generate(im, *args, **kwargs)

    return self.prompt_inference(im, bboxes, points, labels, masks, multimask_output)

postprocess

postprocess(preds, img, orig_imgs)

Post-processes SAM's inference outputs to generate object detection masks and bounding boxes.

This method scales masks and boxes to the original image size and applies a threshold to the mask predictions. It leverages SAM's advanced architecture for real-time, promptable segmentation tasks.

Parameters:

NameTypeDescriptionDefault
predsTuple[Tensor]

The output from SAM model inference, containing: - pred_masks (torch.Tensor): Predicted masks with shape (N, 1, H, W). - pred_scores (torch.Tensor): Confidence scores for each mask with shape (N, 1). - pred_bboxes (torch.Tensor, optional): Predicted bounding boxes if segment_all is True.

required
imgTensor

The processed input image tensor with shape (C, H, W).

required
orig_imgsList[ndarray] | Tensor

The original, unprocessed images.

required

Returns:

TypeDescription
List[Results]

List of Results objects containing detection masks, bounding boxes, and other metadata for each processed image.

Examples:

>>> predictor = Predictor()
>>> preds = predictor.inference(img)
>>> results = predictor.postprocess(preds, img, orig_imgs)
Source code in ultralytics/models/sam/predict.py
def postprocess(self, preds, img, orig_imgs):
    """
    Post-processes SAM's inference outputs to generate object detection masks and bounding boxes.

    This method scales masks and boxes to the original image size and applies a threshold to the mask
    predictions. It leverages SAM's advanced architecture for real-time, promptable segmentation tasks.

    Args:
        preds (Tuple[torch.Tensor]): The output from SAM model inference, containing:
            - pred_masks (torch.Tensor): Predicted masks with shape (N, 1, H, W).
            - pred_scores (torch.Tensor): Confidence scores for each mask with shape (N, 1).
            - pred_bboxes (torch.Tensor, optional): Predicted bounding boxes if segment_all is True.
        img (torch.Tensor): The processed input image tensor with shape (C, H, W).
        orig_imgs (List[np.ndarray] | torch.Tensor): The original, unprocessed images.

    Returns:
        (List[Results]): List of Results objects containing detection masks, bounding boxes, and other
            metadata for each processed image.

    Examples:
        >>> predictor = Predictor()
        >>> preds = predictor.inference(img)
        >>> results = predictor.postprocess(preds, img, orig_imgs)
    """
    # (N, 1, H, W), (N, 1)
    pred_masks, pred_scores = preds[:2]
    pred_bboxes = preds[2] if self.segment_all else None
    names = dict(enumerate(str(i) for i in range(len(pred_masks))))

    if not isinstance(orig_imgs, list):  # input images are a torch.Tensor, not a list
        orig_imgs = ops.convert_torch2numpy_batch(orig_imgs)

    results = []
    for masks, orig_img, img_path in zip([pred_masks], orig_imgs, self.batch[0]):
        if len(masks) == 0:
            masks = None
        else:
            masks = ops.scale_masks(masks[None].float(), orig_img.shape[:2], padding=False)[0]
            masks = masks > self.model.mask_threshold  # to bool
            if pred_bboxes is not None:
                pred_bboxes = ops.scale_boxes(img.shape[2:], pred_bboxes.float(), orig_img.shape, padding=False)
            else:
                pred_bboxes = batched_mask_to_box(masks)
            # NOTE: SAM models do not return cls info. This `cls` here is just a placeholder for consistency.
            cls = torch.arange(len(pred_masks), dtype=torch.int32, device=pred_masks.device)
            pred_bboxes = torch.cat([pred_bboxes, pred_scores[:, None], cls[:, None]], dim=-1)
        results.append(Results(orig_img, path=img_path, names=names, masks=masks, boxes=pred_bboxes))
    # Reset segment-all mode.
    self.segment_all = False
    return results

pre_transform

pre_transform(im)

Perform initial transformations on the input image for preprocessing.

This method applies transformations such as resizing to prepare the image for further preprocessing. Currently, batched inference is not supported; hence the list length should be 1.

Parameters:

NameTypeDescriptionDefault
imList[ndarray]

List containing a single image in HWC numpy array format.

required

Returns:

TypeDescription
List[ndarray]

List containing the transformed image.

Raises:

TypeDescription
AssertionError

If the input list contains more than one image.

Examples:

>>> predictor = Predictor()
>>> image = np.random.rand(480, 640, 3)  # Single HWC image
>>> transformed = predictor.pre_transform([image])
>>> print(len(transformed))
1
Source code in ultralytics/models/sam/predict.py
def pre_transform(self, im):
    """
    Perform initial transformations on the input image for preprocessing.

    This method applies transformations such as resizing to prepare the image for further preprocessing.
    Currently, batched inference is not supported; hence the list length should be 1.

    Args:
        im (List[np.ndarray]): List containing a single image in HWC numpy array format.

    Returns:
        (List[np.ndarray]): List containing the transformed image.

    Raises:
        AssertionError: If the input list contains more than one image.

    Examples:
        >>> predictor = Predictor()
        >>> image = np.random.rand(480, 640, 3)  # Single HWC image
        >>> transformed = predictor.pre_transform([image])
        >>> print(len(transformed))
        1
    """
    assert len(im) == 1, "SAM model does not currently support batched inference"
    letterbox = LetterBox(self.args.imgsz, auto=False, center=False)
    return [letterbox(image=x) for x in im]

preprocess

preprocess(im)

Preprocess the input image for model inference.

This method prepares the input image by applying transformations and normalization. It supports both torch.Tensor and list of np.ndarray as input formats.

Parameters:

NameTypeDescriptionDefault
imTensor | List[ndarray]

Input image(s) in BCHW tensor format or list of HWC numpy arrays.

required

Returns:

TypeDescription
Tensor

The preprocessed image tensor, normalized and converted to the appropriate dtype.

Examples:

>>> predictor = Predictor()
>>> image = torch.rand(1, 3, 640, 640)
>>> preprocessed_image = predictor.preprocess(image)
Source code in ultralytics/models/sam/predict.py
def preprocess(self, im):
    """
    Preprocess the input image for model inference.

    This method prepares the input image by applying transformations and normalization. It supports both
    torch.Tensor and list of np.ndarray as input formats.

    Args:
        im (torch.Tensor | List[np.ndarray]): Input image(s) in BCHW tensor format or list of HWC numpy arrays.

    Returns:
        (torch.Tensor): The preprocessed image tensor, normalized and converted to the appropriate dtype.

    Examples:
        >>> predictor = Predictor()
        >>> image = torch.rand(1, 3, 640, 640)
        >>> preprocessed_image = predictor.preprocess(image)
    """
    if self.im is not None:
        return self.im
    not_tensor = not isinstance(im, torch.Tensor)
    if not_tensor:
        im = np.stack(self.pre_transform(im))
        im = im[..., ::-1].transpose((0, 3, 1, 2))
        im = np.ascontiguousarray(im)
        im = torch.from_numpy(im)

    im = im.to(self.device)
    im = im.half() if self.model.fp16 else im.float()
    if not_tensor:
        im = (im - self.mean) / self.std
    return im

prompt_inference

prompt_inference(
    im,
    bboxes=None,
    points=None,
    labels=None,
    masks=None,
    multimask_output=False,
)

Performs image segmentation inference based on input cues using SAM's specialized architecture.

This internal function leverages the Segment Anything Model (SAM) for prompt-based, real-time segmentation. It processes various input prompts such as bounding boxes, points, and masks to generate segmentation masks.

Parameters:

NameTypeDescriptionDefault
imTensor

Preprocessed input image tensor with shape (N, C, H, W).

required
bboxesndarray | List | None

Bounding boxes in XYXY format with shape (N, 4).

None
pointsndarray | List | None

Points indicating object locations with shape (N, 2) or (N, num_points, 2), in pixels.

None
labelsndarray | List | None

Point prompt labels with shape (N,) or (N, num_points). 1 for foreground, 0 for background.

None
masksndarray | None

Low-res masks from previous predictions with shape (N, H, W). For SAM, H=W=256.

None
multimask_outputbool

Flag to return multiple masks for ambiguous prompts.

False

Raises:

TypeDescription
AssertionError

If the number of points don't match the number of labels, in case labels were passed.

Returns:

TypeDescription
tuple

Tuple containing: - np.ndarray: Output masks with shape (C, H, W), where C is the number of generated masks. - np.ndarray: Quality scores predicted by the model for each mask, with length C. - np.ndarray: Low-resolution logits with shape (C, H, W) for subsequent inference, where H=W=256.

Examples:

>>> predictor = Predictor()
>>> im = torch.rand(1, 3, 1024, 1024)
>>> bboxes = [[100, 100, 200, 200]]
>>> masks, scores, logits = predictor.prompt_inference(im, bboxes=bboxes)
Source code in ultralytics/models/sam/predict.py
def prompt_inference(self, im, bboxes=None, points=None, labels=None, masks=None, multimask_output=False):
    """
    Performs image segmentation inference based on input cues using SAM's specialized architecture.

    This internal function leverages the Segment Anything Model (SAM) for prompt-based, real-time segmentation.
    It processes various input prompts such as bounding boxes, points, and masks to generate segmentation masks.

    Args:
        im (torch.Tensor): Preprocessed input image tensor with shape (N, C, H, W).
        bboxes (np.ndarray | List | None): Bounding boxes in XYXY format with shape (N, 4).
        points (np.ndarray | List | None): Points indicating object locations with shape (N, 2) or (N, num_points, 2), in pixels.
        labels (np.ndarray | List | None): Point prompt labels with shape (N,) or (N, num_points). 1 for foreground, 0 for background.
        masks (np.ndarray | None): Low-res masks from previous predictions with shape (N, H, W). For SAM, H=W=256.
        multimask_output (bool): Flag to return multiple masks for ambiguous prompts.

    Raises:
        AssertionError: If the number of points don't match the number of labels, in case labels were passed.

    Returns:
        (tuple): Tuple containing:
            - np.ndarray: Output masks with shape (C, H, W), where C is the number of generated masks.
            - np.ndarray: Quality scores predicted by the model for each mask, with length C.
            - np.ndarray: Low-resolution logits with shape (C, H, W) for subsequent inference, where H=W=256.

    Examples:
        >>> predictor = Predictor()
        >>> im = torch.rand(1, 3, 1024, 1024)
        >>> bboxes = [[100, 100, 200, 200]]
        >>> masks, scores, logits = predictor.prompt_inference(im, bboxes=bboxes)
    """
    features = self.get_im_features(im) if self.features is None else self.features

    bboxes, points, labels, masks = self._prepare_prompts(im.shape[2:], bboxes, points, labels, masks)
    points = (points, labels) if points is not None else None
    # Embed prompts
    sparse_embeddings, dense_embeddings = self.model.prompt_encoder(points=points, boxes=bboxes, masks=masks)

    # Predict masks
    pred_masks, pred_scores = self.model.mask_decoder(
        image_embeddings=features,
        image_pe=self.model.prompt_encoder.get_dense_pe(),
        sparse_prompt_embeddings=sparse_embeddings,
        dense_prompt_embeddings=dense_embeddings,
        multimask_output=multimask_output,
    )

    # (N, d, H, W) --> (N*d, H, W), (N, d) --> (N*d, )
    # `d` could be 1 or 3 depends on `multimask_output`.
    return pred_masks.flatten(0, 1), pred_scores.flatten(0, 1)

remove_small_regions staticmethod

remove_small_regions(masks, min_area=0, nms_thresh=0.7)

Remove small disconnected regions and holes from segmentation masks.

This function performs post-processing on segmentation masks generated by the Segment Anything Model (SAM). It removes small disconnected regions and holes from the input masks, and then performs Non-Maximum Suppression (NMS) to eliminate any newly created duplicate boxes.

Parameters:

NameTypeDescriptionDefault
masksTensor

Segmentation masks to be processed, with shape (N, H, W) where N is the number of masks, H is height, and W is width.

required
min_areaint

Minimum area threshold for removing disconnected regions and holes. Regions smaller than this will be removed.

0
nms_threshfloat

IoU threshold for the NMS algorithm to remove duplicate boxes.

0.7

Returns:

TypeDescription
tuple
  • new_masks (torch.Tensor): Processed masks with small regions removed, shape (N, H, W).
  • keep (List[int]): Indices of remaining masks after NMS, for filtering corresponding boxes.

Examples:

>>> masks = torch.rand(5, 640, 640) > 0.5  # 5 random binary masks
>>> new_masks, keep = remove_small_regions(masks, min_area=100, nms_thresh=0.7)
>>> print(f"Original masks: {masks.shape}, Processed masks: {new_masks.shape}")
>>> print(f"Indices of kept masks: {keep}")
Source code in ultralytics/models/sam/predict.py
@staticmethod
def remove_small_regions(masks, min_area=0, nms_thresh=0.7):
    """
    Remove small disconnected regions and holes from segmentation masks.

    This function performs post-processing on segmentation masks generated by the Segment Anything Model (SAM).
    It removes small disconnected regions and holes from the input masks, and then performs Non-Maximum
    Suppression (NMS) to eliminate any newly created duplicate boxes.

    Args:
        masks (torch.Tensor): Segmentation masks to be processed, with shape (N, H, W) where N is the number of
            masks, H is height, and W is width.
        min_area (int): Minimum area threshold for removing disconnected regions and holes. Regions smaller than
            this will be removed.
        nms_thresh (float): IoU threshold for the NMS algorithm to remove duplicate boxes.

    Returns:
        (tuple):
            - new_masks (torch.Tensor): Processed masks with small regions removed, shape (N, H, W).
            - keep (List[int]): Indices of remaining masks after NMS, for filtering corresponding boxes.

    Examples:
        >>> masks = torch.rand(5, 640, 640) > 0.5  # 5 random binary masks
        >>> new_masks, keep = remove_small_regions(masks, min_area=100, nms_thresh=0.7)
        >>> print(f"Original masks: {masks.shape}, Processed masks: {new_masks.shape}")
        >>> print(f"Indices of kept masks: {keep}")
    """
    import torchvision  # scope for faster 'import ultralytics'

    if len(masks) == 0:
        return masks

    # Filter small disconnected regions and holes
    new_masks = []
    scores = []
    for mask in masks:
        mask = mask.cpu().numpy().astype(np.uint8)
        mask, changed = remove_small_regions(mask, min_area, mode="holes")
        unchanged = not changed
        mask, changed = remove_small_regions(mask, min_area, mode="islands")
        unchanged = unchanged and not changed

        new_masks.append(torch.as_tensor(mask).unsqueeze(0))
        # Give score=0 to changed masks and 1 to unchanged masks so NMS prefers masks not needing postprocessing
        scores.append(float(unchanged))

    # Recalculate boxes and remove any new duplicates
    new_masks = torch.cat(new_masks, dim=0)
    boxes = batched_mask_to_box(new_masks)
    keep = torchvision.ops.nms(boxes.float(), torch.as_tensor(scores), nms_thresh)

    return new_masks[keep].to(device=masks.device, dtype=masks.dtype), keep

reset_image

reset_image()

Resets the current image and its features, clearing them for subsequent inference.

Source code in ultralytics/models/sam/predict.py
def reset_image(self):
    """Resets the current image and its features, clearing them for subsequent inference."""
    self.im = None
    self.features = None

set_image

set_image(image)

Preprocesses and sets a single image for inference.

This method prepares the model for inference on a single image by setting up the model if not already initialized, configuring the data source, and preprocessing the image for feature extraction. It ensures that only one image is set at a time and extracts image features for subsequent use.

Parameters:

NameTypeDescriptionDefault
imagestr | ndarray

Path to the image file as a string, or a numpy array representing an image read by cv2.

required

Raises:

TypeDescription
AssertionError

If more than one image is attempted to be set.

Examples:

>>> predictor = Predictor()
>>> predictor.set_image("path/to/image.jpg")
>>> predictor.set_image(cv2.imread("path/to/image.jpg"))
Notes
  • This method should be called before performing inference on a new image.
  • The extracted features are stored in the self.features attribute for later use.
Source code in ultralytics/models/sam/predict.py
def set_image(self, image):
    """
    Preprocesses and sets a single image for inference.

    This method prepares the model for inference on a single image by setting up the model if not already
    initialized, configuring the data source, and preprocessing the image for feature extraction. It
    ensures that only one image is set at a time and extracts image features for subsequent use.

    Args:
        image (str | np.ndarray): Path to the image file as a string, or a numpy array representing
            an image read by cv2.

    Raises:
        AssertionError: If more than one image is attempted to be set.

    Examples:
        >>> predictor = Predictor()
        >>> predictor.set_image("path/to/image.jpg")
        >>> predictor.set_image(cv2.imread("path/to/image.jpg"))

    Notes:
        - This method should be called before performing inference on a new image.
        - The extracted features are stored in the `self.features` attribute for later use.
    """
    if self.model is None:
        self.setup_model(model=None)
    self.setup_source(image)
    assert len(self.dataset) == 1, "`set_image` only supports setting one image!"
    for batch in self.dataset:
        im = self.preprocess(batch[1])
        self.features = self.get_im_features(im)
        break

set_prompts

set_prompts(prompts)

Sets prompts for subsequent inference operations.

Source code in ultralytics/models/sam/predict.py
def set_prompts(self, prompts):
    """Sets prompts for subsequent inference operations."""
    self.prompts = prompts

setup_model

setup_model(model, verbose=True)

Initializes the Segment Anything Model (SAM) for inference.

This method sets up the SAM model by allocating it to the appropriate device and initializing the necessary parameters for image normalization and other Ultralytics compatibility settings.

Parameters:

NameTypeDescriptionDefault
modelModule

A pre-trained SAM model. If None, a model will be built based on configuration.

required
verbosebool

If True, prints selected device information.

True

Examples:

>>> predictor = Predictor()
>>> predictor.setup_model(model=sam_model, verbose=True)
Source code in ultralytics/models/sam/predict.py
def setup_model(self, model, verbose=True):
    """
    Initializes the Segment Anything Model (SAM) for inference.

    This method sets up the SAM model by allocating it to the appropriate device and initializing the necessary
    parameters for image normalization and other Ultralytics compatibility settings.

    Args:
        model (torch.nn.Module): A pre-trained SAM model. If None, a model will be built based on configuration.
        verbose (bool): If True, prints selected device information.

    Examples:
        >>> predictor = Predictor()
        >>> predictor.setup_model(model=sam_model, verbose=True)
    """
    device = select_device(self.args.device, verbose=verbose)
    if model is None:
        model = self.get_model()
    model.eval()
    self.model = model.to(device)
    self.device = device
    self.mean = torch.tensor([123.675, 116.28, 103.53]).view(-1, 1, 1).to(device)
    self.std = torch.tensor([58.395, 57.12, 57.375]).view(-1, 1, 1).to(device)

    # Ultralytics compatibility settings
    self.model.pt = False
    self.model.triton = False
    self.model.stride = 32
    self.model.fp16 = False
    self.done_warmup = True

setup_source

setup_source(source)

Sets up the data source for inference.

This method configures the data source from which images will be fetched for inference. It supports various input types such as image files, directories, video files, and other compatible data sources.

Parameters:

NameTypeDescriptionDefault
sourcestr | Path | None

The path or identifier for the image data source. Can be a file path, directory path, URL, or other supported source types.

required

Examples:

>>> predictor = Predictor()
>>> predictor.setup_source("path/to/images")
>>> predictor.setup_source("video.mp4")
>>> predictor.setup_source(None)  # Uses default source if available
Notes
  • If source is None, the method may use a default source if configured.
  • The method adapts to different source types and prepares them for subsequent inference steps.
  • Supported source types may include local files, directories, URLs, and video streams.
Source code in ultralytics/models/sam/predict.py
def setup_source(self, source):
    """
    Sets up the data source for inference.

    This method configures the data source from which images will be fetched for inference. It supports
    various input types such as image files, directories, video files, and other compatible data sources.

    Args:
        source (str | Path | None): The path or identifier for the image data source. Can be a file path,
            directory path, URL, or other supported source types.

    Examples:
        >>> predictor = Predictor()
        >>> predictor.setup_source("path/to/images")
        >>> predictor.setup_source("video.mp4")
        >>> predictor.setup_source(None)  # Uses default source if available

    Notes:
        - If source is None, the method may use a default source if configured.
        - The method adapts to different source types and prepares them for subsequent inference steps.
        - Supported source types may include local files, directories, URLs, and video streams.
    """
    if source is not None:
        super().setup_source(source)





ultralytics.models.sam.predict.SAM2Predictor

SAM2Predictor(cfg=DEFAULT_CFG, overrides=None, _callbacks=None)

Bases: Predictor

SAM2Predictor class for advanced image segmentation using Segment Anything Model 2 architecture.

This class extends the base Predictor class to implement SAM2-specific functionality for image segmentation tasks. It provides methods for model initialization, feature extraction, and prompt-based inference.

Attributes:

NameTypeDescription
_bb_feat_sizesList[Tuple[int, int]]

Feature sizes for different backbone levels.

modelModule

The loaded SAM2 model.

devicedevice

The device (CPU or GPU) on which the model is loaded.

featuresDict[str, Tensor]

Cached image features for efficient inference.

segment_allbool

Flag to indicate if all segments should be predicted.

promptsDict

Dictionary to store various types of prompts for inference.

Methods:

NameDescription
get_model

Retrieves and initializes the SAM2 model.

prompt_inference

Performs image segmentation inference based on various prompts.

set_image

Preprocesses and sets a single image for inference.

get_im_features

Extracts and processes image features using SAM2's image encoder.

Examples:

>>> predictor = SAM2Predictor(cfg)
>>> predictor.set_image("path/to/image.jpg")
>>> bboxes = [[100, 100, 200, 200]]
>>> masks, scores, _ = predictor.prompt_inference(predictor.im, bboxes=bboxes)
>>> print(f"Predicted {len(masks)} masks with average score {scores.mean():.2f}")

Sets up the Predictor object for SAM (Segment Anything Model) and applies any configuration overrides or callbacks provided. Initializes task-specific settings for SAM, such as retina_masks being set to True for optimal results.

Parameters:

NameTypeDescriptionDefault
cfgDict

Configuration dictionary containing default settings.

DEFAULT_CFG
overridesDict | None

Dictionary of values to override default configuration.

None
_callbacksDict | None

Dictionary of callback functions to customize behavior.

None

Examples:

>>> predictor = Predictor(cfg=DEFAULT_CFG)
>>> predictor = Predictor(overrides={"imgsz": 640})
>>> predictor = Predictor(_callbacks={"on_predict_start": custom_callback})
Source code in ultralytics/models/sam/predict.py
def __init__(self, cfg=DEFAULT_CFG, overrides=None, _callbacks=None):
    """
    Initialize the Predictor with configuration, overrides, and callbacks.

    Sets up the Predictor object for SAM (Segment Anything Model) and applies any configuration overrides or
    callbacks provided. Initializes task-specific settings for SAM, such as retina_masks being set to True
    for optimal results.

    Args:
        cfg (Dict): Configuration dictionary containing default settings.
        overrides (Dict | None): Dictionary of values to override default configuration.
        _callbacks (Dict | None): Dictionary of callback functions to customize behavior.

    Examples:
        >>> predictor = Predictor(cfg=DEFAULT_CFG)
        >>> predictor = Predictor(overrides={"imgsz": 640})
        >>> predictor = Predictor(_callbacks={"on_predict_start": custom_callback})
    """
    if overrides is None:
        overrides = {}
    overrides.update(dict(task="segment", mode="predict"))
    super().__init__(cfg, overrides, _callbacks)
    self.args.retina_masks = True
    self.im = None
    self.features = None
    self.prompts = {}
    self.segment_all = False

get_im_features

get_im_features(im)

Extracts image features from the SAM image encoder for subsequent processing.

Source code in ultralytics/models/sam/predict.py
def get_im_features(self, im):
    """Extracts image features from the SAM image encoder for subsequent processing."""
    assert (
        isinstance(self.imgsz, (tuple, list)) and self.imgsz[0] == self.imgsz[1]
    ), f"SAM 2 models only support square image size, but got {self.imgsz}."
    self.model.set_imgsz(self.imgsz)
    self._bb_feat_sizes = [[x // (4 * i) for x in self.imgsz] for i in [1, 2, 4]]

    backbone_out = self.model.forward_image(im)
    _, vision_feats, _, _ = self.model._prepare_backbone_features(backbone_out)
    if self.model.directly_add_no_mem_embed:
        vision_feats[-1] = vision_feats[-1] + self.model.no_mem_embed
    feats = [
        feat.permute(1, 2, 0).view(1, -1, *feat_size)
        for feat, feat_size in zip(vision_feats[::-1], self._bb_feat_sizes[::-1])
    ][::-1]
    return {"image_embed": feats[-1], "high_res_feats": feats[:-1]}

get_model

get_model()

Retrieves and initializes the Segment Anything Model 2 (SAM2) for image segmentation tasks.

Source code in ultralytics/models/sam/predict.py
def get_model(self):
    """Retrieves and initializes the Segment Anything Model 2 (SAM2) for image segmentation tasks."""
    return build_sam(self.args.model)

prompt_inference

prompt_inference(
    im,
    bboxes=None,
    points=None,
    labels=None,
    masks=None,
    multimask_output=False,
    img_idx=-1,
)

Performs image segmentation inference based on various prompts using SAM2 architecture.

This method leverages the Segment Anything Model 2 (SAM2) to generate segmentation masks for input images based on provided prompts such as bounding boxes, points, or existing masks. It supports both single and multi-object prediction scenarios.

Parameters:

NameTypeDescriptionDefault
imTensor

Preprocessed input image tensor with shape (N, C, H, W).

required
bboxesndarray | List[List[float]] | None

Bounding boxes in XYXY format with shape (N, 4).

None
pointsndarray | List[List[float]] | None

Object location points with shape (N, 2), in pixels.

None
labelsndarray | List[int] | None

Point prompt labels with shape (N,). 1 = foreground, 0 = background.

None
masksndarray | None

Low-resolution masks from previous predictions with shape (N, H, W).

None
multimask_outputbool

Flag to return multiple masks for ambiguous prompts.

False
img_idxint

Index of the image in the batch to process.

-1

Returns:

TypeDescription
tuple

Tuple containing: - np.ndarray: Output masks with shape (C, H, W), where C is the number of generated masks. - np.ndarray: Quality scores for each mask, with length C. - np.ndarray: Low-resolution logits with shape (C, 256, 256) for subsequent inference.

Examples:

>>> predictor = SAM2Predictor(cfg)
>>> image = torch.rand(1, 3, 640, 640)
>>> bboxes = [[100, 100, 200, 200]]
>>> masks, scores, logits = predictor.prompt_inference(image, bboxes=bboxes)
>>> print(f"Generated {masks.shape[0]} masks with average score {scores.mean():.2f}")
Notes
  • The method supports batched inference for multiple objects when points or bboxes are provided.
  • Input prompts (bboxes, points) are automatically scaled to match the input image dimensions.
  • When both bboxes and points are provided, they are merged into a single 'points' input for the model.
References
  • SAM2 Paper: [Add link to SAM2 paper when available]
Source code in ultralytics/models/sam/predict.py
def prompt_inference(
    self,
    im,
    bboxes=None,
    points=None,
    labels=None,
    masks=None,
    multimask_output=False,
    img_idx=-1,
):
    """
    Performs image segmentation inference based on various prompts using SAM2 architecture.

    This method leverages the Segment Anything Model 2 (SAM2) to generate segmentation masks for input images
    based on provided prompts such as bounding boxes, points, or existing masks. It supports both single and
    multi-object prediction scenarios.

    Args:
        im (torch.Tensor): Preprocessed input image tensor with shape (N, C, H, W).
        bboxes (np.ndarray | List[List[float]] | None): Bounding boxes in XYXY format with shape (N, 4).
        points (np.ndarray | List[List[float]] | None): Object location points with shape (N, 2), in pixels.
        labels (np.ndarray | List[int] | None): Point prompt labels with shape (N,). 1 = foreground, 0 = background.
        masks (np.ndarray | None): Low-resolution masks from previous predictions with shape (N, H, W).
        multimask_output (bool): Flag to return multiple masks for ambiguous prompts.
        img_idx (int): Index of the image in the batch to process.

    Returns:
        (tuple): Tuple containing:
            - np.ndarray: Output masks with shape (C, H, W), where C is the number of generated masks.
            - np.ndarray: Quality scores for each mask, with length C.
            - np.ndarray: Low-resolution logits with shape (C, 256, 256) for subsequent inference.

    Examples:
        >>> predictor = SAM2Predictor(cfg)
        >>> image = torch.rand(1, 3, 640, 640)
        >>> bboxes = [[100, 100, 200, 200]]
        >>> masks, scores, logits = predictor.prompt_inference(image, bboxes=bboxes)
        >>> print(f"Generated {masks.shape[0]} masks with average score {scores.mean():.2f}")

    Notes:
        - The method supports batched inference for multiple objects when points or bboxes are provided.
        - Input prompts (bboxes, points) are automatically scaled to match the input image dimensions.
        - When both bboxes and points are provided, they are merged into a single 'points' input for the model.

    References:
        - SAM2 Paper: [Add link to SAM2 paper when available]
    """
    features = self.get_im_features(im) if self.features is None else self.features

    bboxes, points, labels, masks = self._prepare_prompts(im.shape[2:], bboxes, points, labels, masks)
    points = (points, labels) if points is not None else None

    sparse_embeddings, dense_embeddings = self.model.sam_prompt_encoder(
        points=points,
        boxes=None,
        masks=masks,
    )
    # Predict masks
    batched_mode = points is not None and points[0].shape[0] > 1  # multi object prediction
    high_res_features = [feat_level[img_idx].unsqueeze(0) for feat_level in features["high_res_feats"]]
    pred_masks, pred_scores, _, _ = self.model.sam_mask_decoder(
        image_embeddings=features["image_embed"][img_idx].unsqueeze(0),
        image_pe=self.model.sam_prompt_encoder.get_dense_pe(),
        sparse_prompt_embeddings=sparse_embeddings,
        dense_prompt_embeddings=dense_embeddings,
        multimask_output=multimask_output,
        repeat_image=batched_mode,
        high_res_features=high_res_features,
    )
    # (N, d, H, W) --> (N*d, H, W), (N, d) --> (N*d, )
    # `d` could be 1 or 3 depends on `multimask_output`.
    return pred_masks.flatten(0, 1), pred_scores.flatten(0, 1)

set_image

set_image(image)

Preprocesses and sets a single image for inference using the SAM2 model.

This method initializes the model if not already done, configures the data source to the specified image, and preprocesses the image for feature extraction. It supports setting only one image at a time.

Parameters:

NameTypeDescriptionDefault
imagestr | ndarray

Path to the image file as a string, or a numpy array representing the image.

required

Raises:

TypeDescription
AssertionError

If more than one image is attempted to be set.

Examples:

>>> predictor = SAM2Predictor()
>>> predictor.set_image("path/to/image.jpg")
>>> predictor.set_image(np.array([...]))  # Using a numpy array
Notes
  • This method must be called before performing any inference on a new image.
  • The method caches the extracted features for efficient subsequent inferences on the same image.
  • Only one image can be set at a time. To process multiple images, call this method for each new image.
Source code in ultralytics/models/sam/predict.py
def set_image(self, image):
    """
    Preprocesses and sets a single image for inference using the SAM2 model.

    This method initializes the model if not already done, configures the data source to the specified image,
    and preprocesses the image for feature extraction. It supports setting only one image at a time.

    Args:
        image (str | np.ndarray): Path to the image file as a string, or a numpy array representing the image.

    Raises:
        AssertionError: If more than one image is attempted to be set.

    Examples:
        >>> predictor = SAM2Predictor()
        >>> predictor.set_image("path/to/image.jpg")
        >>> predictor.set_image(np.array([...]))  # Using a numpy array

    Notes:
        - This method must be called before performing any inference on a new image.
        - The method caches the extracted features for efficient subsequent inferences on the same image.
        - Only one image can be set at a time. To process multiple images, call this method for each new image.
    """
    if self.model is None:
        self.setup_model(model=None)
    self.setup_source(image)
    assert len(self.dataset) == 1, "`set_image` only supports setting one image!"
    for batch in self.dataset:
        im = self.preprocess(batch[1])
        self.features = self.get_im_features(im)
        break



📅 Created 11 months ago ✏️ Updated 1 month ago