Reference for ultralytics/utils/ops.py

def segment2box(segment, width=640, height=640):
    """
    Convert 1 segment label to 1 box label, applying inside-image constraint, i.e. (xy1, xy2, ...) to (xyxy).

    Args:
        segment (torch.Tensor): the segment label
        width (int): the width of the image. Defaults to 640
        height (int): The height of the image. Defaults to 640

    Returns:
        (np.ndarray): the minimum and maximum x and y values of the segment.
    """
    # Convert 1 segment label to 1 box label, applying inside-image constraint, i.e. (xy1, xy2, ...) to (xyxy)
    x, y = segment.T  # segment xy
    inside = (x >= 0) & (y >= 0) & (x <= width) & (y <= height)
    x, y, = x[inside], y[inside]
    return np.array([x.min(), y.min(), x.max(), y.max()], dtype=segment.dtype) if any(x) else np.zeros(
        4, dtype=segment.dtype)  # xyxy

def scale_boxes(img1_shape, boxes, img0_shape, ratio_pad=None, padding=True):
    """
    Rescales bounding boxes (in the format of xyxy) from the shape of the image they were originally specified in
    (img1_shape) to the shape of a different image (img0_shape).

    Args:
        img1_shape (tuple): The shape of the image that the bounding boxes are for, in the format of (height, width).
        boxes (torch.Tensor): the bounding boxes of the objects in the image, in the format of (x1, y1, x2, y2)
        img0_shape (tuple): the shape of the target image, in the format of (height, width).
        ratio_pad (tuple): a tuple of (ratio, pad) for scaling the boxes. If not provided, the ratio and pad will be
            calculated based on the size difference between the two images.
        padding (bool): If True, assuming the boxes is based on image augmented by yolo style. If False then do regular
            rescaling.

    Returns:
        boxes (torch.Tensor): The scaled bounding boxes, in the format of (x1, y1, x2, y2)
    """
    if ratio_pad is None:  # calculate from img0_shape
        gain = min(img1_shape[0] / img0_shape[0], img1_shape[1] / img0_shape[1])  # gain  = old / new
        pad = round((img1_shape[1] - img0_shape[1] * gain) / 2 - 0.1), round(
            (img1_shape[0] - img0_shape[0] * gain) / 2 - 0.1)  # wh padding
    else:
        gain = ratio_pad[0][0]
        pad = ratio_pad[1]

    if padding:
        boxes[..., [0, 2]] -= pad[0]  # x padding
        boxes[..., [1, 3]] -= pad[1]  # y padding
    boxes[..., :4] /= gain
    clip_boxes(boxes, img0_shape)
    return boxes

def make_divisible(x, divisor):
    """
    Returns the nearest number that is divisible by the given divisor.

    Args:
        x (int): The number to make divisible.
        divisor (int | torch.Tensor): The divisor.

    Returns:
        (int): The nearest number divisible by the divisor.
    """
    if isinstance(divisor, torch.Tensor):
        divisor = int(divisor.max())  # to int
    return math.ceil(x / divisor) * divisor

def non_max_suppression(
        prediction,
        conf_thres=0.25,
        iou_thres=0.45,
        classes=None,
        agnostic=False,
        multi_label=False,
        labels=(),
        max_det=300,
        nc=0,  # number of classes (optional)
        max_time_img=0.05,
        max_nms=30000,
        max_wh=7680,
):
    """
    Perform non-maximum suppression (NMS) on a set of boxes, with support for masks and multiple labels per box.

    Args:
        prediction (torch.Tensor): A tensor of shape (batch_size, num_classes + 4 + num_masks, num_boxes)
            containing the predicted boxes, classes, and masks. The tensor should be in the format
            output by a model, such as YOLO.
        conf_thres (float): The confidence threshold below which boxes will be filtered out.
            Valid values are between 0.0 and 1.0.
        iou_thres (float): The IoU threshold below which boxes will be filtered out during NMS.
            Valid values are between 0.0 and 1.0.
        classes (List[int]): A list of class indices to consider. If None, all classes will be considered.
        agnostic (bool): If True, the model is agnostic to the number of classes, and all
            classes will be considered as one.
        multi_label (bool): If True, each box may have multiple labels.
        labels (List[List[Union[int, float, torch.Tensor]]]): A list of lists, where each inner
            list contains the apriori labels for a given image. The list should be in the format
            output by a dataloader, with each label being a tuple of (class_index, x1, y1, x2, y2).
        max_det (int): The maximum number of boxes to keep after NMS.
        nc (int, optional): The number of classes output by the model. Any indices after this will be considered masks.
        max_time_img (float): The maximum time (seconds) for processing one image.
        max_nms (int): The maximum number of boxes into torchvision.ops.nms().
        max_wh (int): The maximum box width and height in pixels

    Returns:
        (List[torch.Tensor]): A list of length batch_size, where each element is a tensor of
            shape (num_boxes, 6 + num_masks) containing the kept boxes, with columns
            (x1, y1, x2, y2, confidence, class, mask1, mask2, ...).
    """

    # Checks
    assert 0 <= conf_thres <= 1, f'Invalid Confidence threshold {conf_thres}, valid values are between 0.0 and 1.0'
    assert 0 <= iou_thres <= 1, f'Invalid IoU {iou_thres}, valid values are between 0.0 and 1.0'
    if isinstance(prediction, (list, tuple)):  # YOLOv8 model in validation model, output = (inference_out, loss_out)
        prediction = prediction[0]  # select only inference output

    device = prediction.device
    mps = 'mps' in device.type  # Apple MPS
    if mps:  # MPS not fully supported yet, convert tensors to CPU before NMS
        prediction = prediction.cpu()
    bs = prediction.shape[0]  # batch size
    nc = nc or (prediction.shape[1] - 4)  # number of classes
    nm = prediction.shape[1] - nc - 4
    mi = 4 + nc  # mask start index
    xc = prediction[:, 4:mi].amax(1) > conf_thres  # candidates

    # Settings
    # min_wh = 2  # (pixels) minimum box width and height
    time_limit = 0.5 + max_time_img * bs  # seconds to quit after
    multi_label &= nc > 1  # multiple labels per box (adds 0.5ms/img)

    prediction = prediction.transpose(-1, -2)  # shape(1,84,6300) to shape(1,6300,84)
    prediction[..., :4] = xywh2xyxy(prediction[..., :4])  # xywh to xyxy

    t = time.time()
    output = [torch.zeros((0, 6 + nm), device=prediction.device)] * bs
    for xi, x in enumerate(prediction):  # image index, image inference
        # Apply constraints
        # x[((x[:, 2:4] < min_wh) | (x[:, 2:4] > max_wh)).any(1), 4] = 0  # width-height
        x = x[xc[xi]]  # confidence

        # Cat apriori labels if autolabelling
        if labels and len(labels[xi]):
            lb = labels[xi]
            v = torch.zeros((len(lb), nc + nm + 4), device=x.device)
            v[:, :4] = xywh2xyxy(lb[:, 1:5])  # box
            v[range(len(lb)), lb[:, 0].long() + 4] = 1.0  # cls
            x = torch.cat((x, v), 0)

        # If none remain process next image
        if not x.shape[0]:
            continue

        # Detections matrix nx6 (xyxy, conf, cls)
        box, cls, mask = x.split((4, nc, nm), 1)

        if multi_label:
            i, j = torch.where(cls > conf_thres)
            x = torch.cat((box[i], x[i, 4 + j, None], j[:, None].float(), mask[i]), 1)
        else:  # best class only
            conf, j = cls.max(1, keepdim=True)
            x = torch.cat((box, conf, j.float(), mask), 1)[conf.view(-1) > conf_thres]

        # Filter by class
        if classes is not None:
            x = x[(x[:, 5:6] == torch.tensor(classes, device=x.device)).any(1)]

        # Check shape
        n = x.shape[0]  # number of boxes
        if not n:  # no boxes
            continue
        if n > max_nms:  # excess boxes
            x = x[x[:, 4].argsort(descending=True)[:max_nms]]  # sort by confidence and remove excess boxes

        # Batched NMS
        c = x[:, 5:6] * (0 if agnostic else max_wh)  # classes
        boxes, scores = x[:, :4] + c, x[:, 4]  # boxes (offset by class), scores
        i = torchvision.ops.nms(boxes, scores, iou_thres)  # NMS
        i = i[:max_det]  # limit detections

        # # Experimental
        # merge = False  # use merge-NMS
        # if merge and (1 < n < 3E3):  # Merge NMS (boxes merged using weighted mean)
        #     # Update boxes as boxes(i,4) = weights(i,n) * boxes(n,4)
        #     from .metrics import box_iou
        #     iou = box_iou(boxes[i], boxes) > iou_thres  # iou matrix
        #     weights = iou * scores[None]  # box weights
        #     x[i, :4] = torch.mm(weights, x[:, :4]).float() / weights.sum(1, keepdim=True)  # merged boxes
        #     redundant = True  # require redundant detections
        #     if redundant:
        #         i = i[iou.sum(1) > 1]  # require redundancy

        output[xi] = x[i]
        if mps:
            output[xi] = output[xi].to(device)
        if (time.time() - t) > time_limit:
            LOGGER.warning(f'WARNING ⚠️ NMS time limit {time_limit:.3f}s exceeded')
            break  # time limit exceeded

    return output

def clip_boxes(boxes, shape):
    """
    Takes a list of bounding boxes and a shape (height, width) and clips the bounding boxes to the shape.

    Args:
      boxes (torch.Tensor): the bounding boxes to clip
      shape (tuple): the shape of the image
    """
    if isinstance(boxes, torch.Tensor):  # faster individually
        boxes[..., 0].clamp_(0, shape[1])  # x1
        boxes[..., 1].clamp_(0, shape[0])  # y1
        boxes[..., 2].clamp_(0, shape[1])  # x2
        boxes[..., 3].clamp_(0, shape[0])  # y2
    else:  # np.array (faster grouped)
        boxes[..., [0, 2]] = boxes[..., [0, 2]].clip(0, shape[1])  # x1, x2
        boxes[..., [1, 3]] = boxes[..., [1, 3]].clip(0, shape[0])  # y1, y2

def clip_coords(coords, shape):
    """
    Clip line coordinates to the image boundaries.

    Args:
        coords (torch.Tensor | numpy.ndarray): A list of line coordinates.
        shape (tuple): A tuple of integers representing the size of the image in the format (height, width).

    Returns:
        (None): The function modifies the input `coordinates` in place, by clipping each coordinate to the image boundaries.
    """
    if isinstance(coords, torch.Tensor):  # faster individually
        coords[..., 0].clamp_(0, shape[1])  # x
        coords[..., 1].clamp_(0, shape[0])  # y
    else:  # np.array (faster grouped)
        coords[..., 0] = coords[..., 0].clip(0, shape[1])  # x
        coords[..., 1] = coords[..., 1].clip(0, shape[0])  # y

def scale_image(masks, im0_shape, ratio_pad=None):
    """
    Takes a mask, and resizes it to the original image size

    Args:
        masks (np.ndarray): resized and padded masks/images, [h, w, num]/[h, w, 3].
        im0_shape (tuple): the original image shape
        ratio_pad (tuple): the ratio of the padding to the original image.

    Returns:
        masks (torch.Tensor): The masks that are being returned.
    """
    # Rescale coordinates (xyxy) from im1_shape to im0_shape
    im1_shape = masks.shape
    if im1_shape[:2] == im0_shape[:2]:
        return masks
    if ratio_pad is None:  # calculate from im0_shape
        gain = min(im1_shape[0] / im0_shape[0], im1_shape[1] / im0_shape[1])  # gain  = old / new
        pad = (im1_shape[1] - im0_shape[1] * gain) / 2, (im1_shape[0] - im0_shape[0] * gain) / 2  # wh padding
    else:
        gain = ratio_pad[0][0]
        pad = ratio_pad[1]
    top, left = int(pad[1]), int(pad[0])  # y, x
    bottom, right = int(im1_shape[0] - pad[1]), int(im1_shape[1] - pad[0])

    if len(masks.shape) < 2:
        raise ValueError(f'"len of masks shape" should be 2 or 3, but got {len(masks.shape)}')
    masks = masks[top:bottom, left:right]
    masks = cv2.resize(masks, (im0_shape[1], im0_shape[0]))
    if len(masks.shape) == 2:
        masks = masks[:, :, None]

    return masks

def xyxy2xywh(x):
    """
    Convert bounding box coordinates from (x1, y1, x2, y2) format to (x, y, width, height) format where (x1, y1) is the
    top-left corner and (x2, y2) is the bottom-right corner.

    Args:
        x (np.ndarray | torch.Tensor): The input bounding box coordinates in (x1, y1, x2, y2) format.

    Returns:
        y (np.ndarray | torch.Tensor): The bounding box coordinates in (x, y, width, height) format.
    """
    assert x.shape[-1] == 4, f'input shape last dimension expected 4 but input shape is {x.shape}'
    y = torch.empty_like(x) if isinstance(x, torch.Tensor) else np.empty_like(x)  # faster than clone/copy
    y[..., 0] = (x[..., 0] + x[..., 2]) / 2  # x center
    y[..., 1] = (x[..., 1] + x[..., 3]) / 2  # y center
    y[..., 2] = x[..., 2] - x[..., 0]  # width
    y[..., 3] = x[..., 3] - x[..., 1]  # height
    return y

def xywh2xyxy(x):
    """
    Convert bounding box coordinates from (x, y, width, height) format to (x1, y1, x2, y2) format where (x1, y1) is the
    top-left corner and (x2, y2) is the bottom-right corner.

    Args:
        x (np.ndarray | torch.Tensor): The input bounding box coordinates in (x, y, width, height) format.

    Returns:
        y (np.ndarray | torch.Tensor): The bounding box coordinates in (x1, y1, x2, y2) format.
    """
    assert x.shape[-1] == 4, f'input shape last dimension expected 4 but input shape is {x.shape}'
    y = torch.empty_like(x) if isinstance(x, torch.Tensor) else np.empty_like(x)  # faster than clone/copy
    dw = x[..., 2] / 2  # half-width
    dh = x[..., 3] / 2  # half-height
    y[..., 0] = x[..., 0] - dw  # top left x
    y[..., 1] = x[..., 1] - dh  # top left y
    y[..., 2] = x[..., 0] + dw  # bottom right x
    y[..., 3] = x[..., 1] + dh  # bottom right y
    return y

def xywhn2xyxy(x, w=640, h=640, padw=0, padh=0):
    """
    Convert normalized bounding box coordinates to pixel coordinates.

    Args:
        x (np.ndarray | torch.Tensor): The bounding box coordinates.
        w (int): Width of the image. Defaults to 640
        h (int): Height of the image. Defaults to 640
        padw (int): Padding width. Defaults to 0
        padh (int): Padding height. Defaults to 0
    Returns:
        y (np.ndarray | torch.Tensor): The coordinates of the bounding box in the format [x1, y1, x2, y2] where
            x1,y1 is the top-left corner, x2,y2 is the bottom-right corner of the bounding box.
    """
    assert x.shape[-1] == 4, f'input shape last dimension expected 4 but input shape is {x.shape}'
    y = torch.empty_like(x) if isinstance(x, torch.Tensor) else np.empty_like(x)  # faster than clone/copy
    y[..., 0] = w * (x[..., 0] - x[..., 2] / 2) + padw  # top left x
    y[..., 1] = h * (x[..., 1] - x[..., 3] / 2) + padh  # top left y
    y[..., 2] = w * (x[..., 0] + x[..., 2] / 2) + padw  # bottom right x
    y[..., 3] = h * (x[..., 1] + x[..., 3] / 2) + padh  # bottom right y
    return y

def xyxy2xywhn(x, w=640, h=640, clip=False, eps=0.0):
    """
    Convert bounding box coordinates from (x1, y1, x2, y2) format to (x, y, width, height, normalized) format.
    x, y, width and height are normalized to image dimensions

    Args:
        x (np.ndarray | torch.Tensor): The input bounding box coordinates in (x1, y1, x2, y2) format.
        w (int): The width of the image. Defaults to 640
        h (int): The height of the image. Defaults to 640
        clip (bool): If True, the boxes will be clipped to the image boundaries. Defaults to False
        eps (float): The minimum value of the box's width and height. Defaults to 0.0

    Returns:
        y (np.ndarray | torch.Tensor): The bounding box coordinates in (x, y, width, height, normalized) format
    """
    if clip:
        clip_boxes(x, (h - eps, w - eps))  # warning: inplace clip
    assert x.shape[-1] == 4, f'input shape last dimension expected 4 but input shape is {x.shape}'
    y = torch.empty_like(x) if isinstance(x, torch.Tensor) else np.empty_like(x)  # faster than clone/copy
    y[..., 0] = ((x[..., 0] + x[..., 2]) / 2) / w  # x center
    y[..., 1] = ((x[..., 1] + x[..., 3]) / 2) / h  # y center
    y[..., 2] = (x[..., 2] - x[..., 0]) / w  # width
    y[..., 3] = (x[..., 3] - x[..., 1]) / h  # height
    return y

def xywh2ltwh(x):
    """
    Convert the bounding box format from [x, y, w, h] to [x1, y1, w, h], where x1, y1 are the top-left coordinates.

    Args:
        x (np.ndarray | torch.Tensor): The input tensor with the bounding box coordinates in the xywh format

    Returns:
        y (np.ndarray | torch.Tensor): The bounding box coordinates in the xyltwh format
    """
    y = x.clone() if isinstance(x, torch.Tensor) else np.copy(x)
    y[..., 0] = x[..., 0] - x[..., 2] / 2  # top left x
    y[..., 1] = x[..., 1] - x[..., 3] / 2  # top left y
    return y

def xyxy2ltwh(x):
    """
    Convert nx4 bounding boxes from [x1, y1, x2, y2] to [x1, y1, w, h], where xy1=top-left, xy2=bottom-right

    Args:
        x (np.ndarray | torch.Tensor): The input tensor with the bounding boxes coordinates in the xyxy format

    Returns:
        y (np.ndarray | torch.Tensor): The bounding box coordinates in the xyltwh format.
    """
    y = x.clone() if isinstance(x, torch.Tensor) else np.copy(x)
    y[..., 2] = x[..., 2] - x[..., 0]  # width
    y[..., 3] = x[..., 3] - x[..., 1]  # height
    return y

def ltwh2xywh(x):
    """
    Convert nx4 boxes from [x1, y1, w, h] to [x, y, w, h] where xy1=top-left, xy=center

    Args:
        x (torch.Tensor): the input tensor

    Returns:
        y (np.ndarray | torch.Tensor): The bounding box coordinates in the xywh format.
    """
    y = x.clone() if isinstance(x, torch.Tensor) else np.copy(x)
    y[..., 0] = x[..., 0] + x[..., 2] / 2  # center x
    y[..., 1] = x[..., 1] + x[..., 3] / 2  # center y
    return y

def xyxyxyxy2xywhr(corners):
    """
    Convert batched Oriented Bounding Boxes (OBB) from [xy1, xy2, xy3, xy4] to [xywh, rotation].

    Args:
        corners (numpy.ndarray | torch.Tensor): Input corners of shape (n, 8).

    Returns:
        (numpy.ndarray | torch.Tensor): Converted data in [cx, cy, w, h, rotation] format of shape (n, 5).
    """
    is_numpy = isinstance(corners, np.ndarray)
    atan2, sqrt = (np.arctan2, np.sqrt) if is_numpy else (torch.atan2, torch.sqrt)

    x1, y1, x2, y2, x3, y3, x4, y4 = corners.T
    cx = (x1 + x3) / 2
    cy = (y1 + y3) / 2
    dx21 = x2 - x1
    dy21 = y2 - y1

    w = sqrt(dx21 ** 2 + dy21 ** 2)
    h = sqrt((x2 - x3) ** 2 + (y2 - y3) ** 2)

    rotation = atan2(-dy21, dx21)
    rotation *= 180.0 / math.pi  # radians to degrees

    return np.vstack((cx, cy, w, h, rotation)).T if is_numpy else torch.stack((cx, cy, w, h, rotation), dim=1)

def xywhr2xyxyxyxy(center):
    """
    Convert batched Oriented Bounding Boxes (OBB) from [xywh, rotation] to [xy1, xy2, xy3, xy4].

    Args:
        center (numpy.ndarray | torch.Tensor): Input data in [cx, cy, w, h, rotation] format of shape (n, 5).

    Returns:
        (numpy.ndarray | torch.Tensor): Converted corner points of shape (n, 8).
    """
    is_numpy = isinstance(center, np.ndarray)
    cos, sin = (np.cos, np.sin) if is_numpy else (torch.cos, torch.sin)

    cx, cy, w, h, rotation = center.T
    rotation *= math.pi / 180.0  # degrees to radians

    dx = w / 2
    dy = h / 2

    cos_rot = cos(rotation)
    sin_rot = sin(rotation)
    dx_cos_rot = dx * cos_rot
    dx_sin_rot = dx * sin_rot
    dy_cos_rot = dy * cos_rot
    dy_sin_rot = dy * sin_rot

    x1 = cx - dx_cos_rot - dy_sin_rot
    y1 = cy + dx_sin_rot - dy_cos_rot
    x2 = cx + dx_cos_rot - dy_sin_rot
    y2 = cy - dx_sin_rot - dy_cos_rot
    x3 = cx + dx_cos_rot + dy_sin_rot
    y3 = cy - dx_sin_rot + dy_cos_rot
    x4 = cx - dx_cos_rot + dy_sin_rot
    y4 = cy + dx_sin_rot + dy_cos_rot

    return np.vstack((x1, y1, x2, y2, x3, y3, x4, y4)).T if is_numpy else torch.stack(
        (x1, y1, x2, y2, x3, y3, x4, y4), dim=1)

def ltwh2xyxy(x):
    """
    It converts the bounding box from [x1, y1, w, h] to [x1, y1, x2, y2] where xy1=top-left, xy2=bottom-right

    Args:
        x (np.ndarray | torch.Tensor): the input image

    Returns:
        y (np.ndarray | torch.Tensor): the xyxy coordinates of the bounding boxes.
    """
    y = x.clone() if isinstance(x, torch.Tensor) else np.copy(x)
    y[..., 2] = x[..., 2] + x[..., 0]  # width
    y[..., 3] = x[..., 3] + x[..., 1]  # height
    return y

def segments2boxes(segments):
    """
    It converts segment labels to box labels, i.e. (cls, xy1, xy2, ...) to (cls, xywh)

    Args:
        segments (list): list of segments, each segment is a list of points, each point is a list of x, y coordinates

    Returns:
        (np.ndarray): the xywh coordinates of the bounding boxes.
    """
    boxes = []
    for s in segments:
        x, y = s.T  # segment xy
        boxes.append([x.min(), y.min(), x.max(), y.max()])  # cls, xyxy
    return xyxy2xywh(np.array(boxes))  # cls, xywh

def resample_segments(segments, n=1000):
    """
    Inputs a list of segments (n,2) and returns a list of segments (n,2) up-sampled to n points each.

    Args:
        segments (list): a list of (n,2) arrays, where n is the number of points in the segment.
        n (int): number of points to resample the segment to. Defaults to 1000

    Returns:
        segments (list): the resampled segments.
    """
    for i, s in enumerate(segments):
        s = np.concatenate((s, s[0:1, :]), axis=0)
        x = np.linspace(0, len(s) - 1, n)
        xp = np.arange(len(s))
        segments[i] = np.concatenate([np.interp(x, xp, s[:, i]) for i in range(2)],
                                     dtype=np.float32).reshape(2, -1).T  # segment xy
    return segments

def crop_mask(masks, boxes):
    """
    It takes a mask and a bounding box, and returns a mask that is cropped to the bounding box.

    Args:
        masks (torch.Tensor): [n, h, w] tensor of masks
        boxes (torch.Tensor): [n, 4] tensor of bbox coordinates in relative point form

    Returns:
        (torch.Tensor): The masks are being cropped to the bounding box.
    """
    n, h, w = masks.shape
    x1, y1, x2, y2 = torch.chunk(boxes[:, :, None], 4, 1)  # x1 shape(n,1,1)
    r = torch.arange(w, device=masks.device, dtype=x1.dtype)[None, None, :]  # rows shape(1,1,w)
    c = torch.arange(h, device=masks.device, dtype=x1.dtype)[None, :, None]  # cols shape(1,h,1)

    return masks * ((r >= x1) * (r < x2) * (c >= y1) * (c < y2))

def process_mask_upsample(protos, masks_in, bboxes, shape):
    """
    Takes the output of the mask head, and applies the mask to the bounding boxes. This produces masks of higher
    quality but is slower.

    Args:
        protos (torch.Tensor): [mask_dim, mask_h, mask_w]
        masks_in (torch.Tensor): [n, mask_dim], n is number of masks after nms
        bboxes (torch.Tensor): [n, 4], n is number of masks after nms
        shape (tuple): the size of the input image (h,w)

    Returns:
        (torch.Tensor): The upsampled masks.
    """
    c, mh, mw = protos.shape  # CHW
    masks = (masks_in @ protos.float().view(c, -1)).sigmoid().view(-1, mh, mw)
    masks = F.interpolate(masks[None], shape, mode='bilinear', align_corners=False)[0]  # CHW
    masks = crop_mask(masks, bboxes)  # CHW
    return masks.gt_(0.5)

def process_mask(protos, masks_in, bboxes, shape, upsample=False):
    """
    Apply masks to bounding boxes using the output of the mask head.

    Args:
        protos (torch.Tensor): A tensor of shape [mask_dim, mask_h, mask_w].
        masks_in (torch.Tensor): A tensor of shape [n, mask_dim], where n is the number of masks after NMS.
        bboxes (torch.Tensor): A tensor of shape [n, 4], where n is the number of masks after NMS.
        shape (tuple): A tuple of integers representing the size of the input image in the format (h, w).
        upsample (bool): A flag to indicate whether to upsample the mask to the original image size. Default is False.

    Returns:
        (torch.Tensor): A binary mask tensor of shape [n, h, w], where n is the number of masks after NMS, and h and w
            are the height and width of the input image. The mask is applied to the bounding boxes.
    """

    c, mh, mw = protos.shape  # CHW
    ih, iw = shape
    masks = (masks_in @ protos.float().view(c, -1)).sigmoid().view(-1, mh, mw)  # CHW

    downsampled_bboxes = bboxes.clone()
    downsampled_bboxes[:, 0] *= mw / iw
    downsampled_bboxes[:, 2] *= mw / iw
    downsampled_bboxes[:, 3] *= mh / ih
    downsampled_bboxes[:, 1] *= mh / ih

    masks = crop_mask(masks, downsampled_bboxes)  # CHW
    if upsample:
        masks = F.interpolate(masks[None], shape, mode='bilinear', align_corners=False)[0]  # CHW
    return masks.gt_(0.5)