overview布局

从上往下解析

__init__.py

from .base import BaseDataset

__init__.py 文件在 Python 中扮演着重要的角色，它是 Python 包结构的一部分。

当一个目录包含 __init__.py 文件时，Python 会将这个目录视为一个包，允许你导入其中的模块和类。这个文件的目的是告诉 Python 解释器，目录内的内容是一个可导入的模块集合，也就是一个包。

在这个特定的例子中，__init__.py 文件是 ultralytics 库（假设是 ultralytics 包）的一部分，它导出了 base.py、build.py 和 dataset.py 中的一些关键类和函数。通过这种方式，用户可以直接从 ultralytics 包中导入这些导出的类和函数，而不需要知道它们在哪个具体的模块里。

例如，用户可以这样导入和使用这些类和函数：

from ultralytics import BaseDataset, YOLODataset, build_yolo_dataset

dataset = BaseDataset()
yolo_dataset = YOLODataset()
dataloader = build_yolo_dataset(dataset)

这种组织方式提高了代码的可读性和可维护性，因为用户只需要记住在包级别上可用的接口，而不是每个单独模块的细节。同时，__init__.py 也可以用来执行一些初始化逻辑，比如设置配置、注册自定义类型等。

__all__

annotator.py

# Ultralytics YOLO 🚀, AGPL-3.0 license

from pathlib import Path

from ultralytics import SAM, YOLO


def auto_annotate(data, det_model="yolov8x.pt", sam_model="sam_b.pt", device="", output_dir=None):
    """
    Automatically annotates images using a YOLO object detection model and a SAM segmentation model.

    Args:
        data (str): Path to a folder containing images to be annotated.
        det_model (str, optional): Pre-trained YOLO detection model. Defaults to 'yolov8x.pt'.
        sam_model (str, optional): Pre-trained SAM segmentation model. Defaults to 'sam_b.pt'.
        device (str, optional): Device to run the models on. Defaults to an empty string (CPU or GPU, if available).
        output_dir (str | None | optional): Directory to save the annotated results.
            Defaults to a 'labels' folder in the same directory as 'data'.

    Example:
        ```python
        from ultralytics.data.annotator import auto_annotate

        auto_annotate(data='ultralytics/assets', det_model='yolov8n.pt', sam_model='mobile_sam.pt')
        ```
    """
    det_model = YOLO(det_model)
    sam_model = SAM(sam_model)

    data = Path(data)
    if not output_dir:
        output_dir = data.parent / f"{data.stem}_auto_annotate_labels"
    Path(output_dir).mkdir(exist_ok=True, parents=True)

    det_results = det_model(data, stream=True, device=device)

    for result in det_results:
        class_ids = result.boxes.cls.int().tolist()  # noqa
        if len(class_ids):
            boxes = result.boxes.xyxy  # Boxes object for bbox outputs
            sam_results = sam_model(result.orig_img, bboxes=boxes, verbose=False, save=False, device=device)
            segments = sam_results[0].masks.xyn  # noqa

            with open(f"{Path(output_dir) / Path(result.path).stem}.txt", "w") as f:
                for i in range(len(segments)):
                    s = segments[i]
                    if len(s) == 0:
                        continue
                    segment = map(str, segments[i].reshape(-1).tolist())
                    f.write(f"{class_ids[i]} " + " ".join(segment) + "\n")

augment.py

数据增强

class BaseTransform

# TODO: we might need a BaseTransform to make all these augments be compatible with both classification and semantic
class BaseTransform:
    """
    Base class for image transformations.

    This is a generic transformation class that can be extended for specific image processing needs.
    The class is designed to be compatible with both classification and semantic segmentation tasks.

    Methods:
        __init__: Initializes the BaseTransform object.
        apply_image: Applies image transformation to labels.
        apply_instances: Applies transformations to object instances in labels.
        apply_semantic: Applies semantic segmentation to an image.
        __call__: Applies all label transformations to an image, instances, and semantic masks.
    """

    def __init__(self) -> None:
        """Initializes the BaseTransform object."""
        pass

    def apply_image(self, labels):
        """Applies image transformations to labels."""
        pass

    def apply_instances(self, labels):
        """Applies transformations to object instances in labels."""
        pass

    def apply_semantic(self, labels):
        """Applies semantic segmentation to an image."""
        pass

    def __call__(self, labels):
        """Applies all label transformations to an image, instances, and semantic masks."""
        self.apply_image(labels)
        self.apply_instances(labels)
        self.apply_semantic(labels)

class Compose

class Compose:
    """Class for composing multiple image transformations."""

    def __init__(self, transforms):
        """Initializes the Compose object with a list of transforms."""
        self.transforms = transforms if isinstance(transforms, list) else [transforms]

    def __call__(self, data):
        """Applies a series of transformations to input data."""
        for t in self.transforms:
            data = t(data)
        return data

    def append(self, transform):
        """Appends a new transform to the existing list of transforms."""
        self.transforms.append(transform)

    def insert(self, index, transform):
        """Inserts a new transform to the existing list of transforms."""
        self.transforms.insert(index, transform)

    def __getitem__(self, index: Union[list, int]) -> "Compose":
        """Retrieve a specific transform or a set of transforms using indexing."""
        assert isinstance(index, (int, list)), f"The indices should be either list or int type but got {type(index)}"
        index = [index] if isinstance(index, int) else index
        return Compose([self.transforms[i] for i in index])

    def __setitem__(self, index: Union[list, int], value: Union[list, int]) -> None:
        """Retrieve a specific transform or a set of transforms using indexing."""
        assert isinstance(index, (int, list)), f"The indices should be either list or int type but got {type(index)}"
        if isinstance(index, list):
            assert isinstance(
                value, list
            ), f"The indices should be the same type as values, but got {type(index)} and {type(value)}"
        if isinstance(index, int):
            index, value = [index], [value]
        for i, v in zip(index, value):
            assert i < len(self.transforms), f"list index {i} out of range {len(self.transforms)}."
            self.transforms[i] = v

    def tolist(self):
        """Converts the list of transforms to a standard Python list."""
        return self.transforms

    def __repr__(self):
        """Returns a string representation of the object."""
        return f"{self.__class__.__name__}({', '.join([f'{t}' for t in self.transforms])})"

class BaseMixTransform

class BaseMixTransform:
    """
    Class for base mix (MixUp/Mosaic) transformations.

    This implementation is from mmyolo.
    """

    def __init__(self, dataset, pre_transform=None, p=0.0) -> None:
        """Initializes the BaseMixTransform object with dataset, pre_transform, and probability."""
        self.dataset = dataset
        self.pre_transform = pre_transform
        self.p = p

    def __call__(self, labels):
        """Applies pre-processing transforms and mixup/mosaic transforms to labels data."""
        if random.uniform(0, 1) > self.p:
            return labels

        # Get index of one or three other images
        indexes = self.get_indexes()
        if isinstance(indexes, int):
            indexes = [indexes]

        # Get images information will be used for Mosaic or MixUp
        mix_labels = [self.dataset.get_image_and_label(i) for i in indexes]

        if self.pre_transform is not None:
            for i, data in enumerate(mix_labels):
                mix_labels[i] = self.pre_transform(data)
        labels["mix_labels"] = mix_labels

        # Update cls and texts
        labels = self._update_label_text(labels)
        # Mosaic or MixUp
        labels = self._mix_transform(labels)
        labels.pop("mix_labels", None)
        return labels

    def _mix_transform(self, labels):
        """Applies MixUp or Mosaic augmentation to the label dictionary."""
        raise NotImplementedError

    def get_indexes(self):
        """Gets a list of shuffled indexes for mosaic augmentation."""
        raise NotImplementedError

    def _update_label_text(self, labels):
        """Update label text."""
        if "texts" not in labels:
            return labels

        mix_texts = sum([labels["texts"]] + [x["texts"] for x in labels["mix_labels"]], [])
        mix_texts = list({tuple(x) for x in mix_texts})
        text2id = {text: i for i, text in enumerate(mix_texts)}

        for label in [labels] + labels["mix_labels"]:
            for i, cls in enumerate(label["cls"].squeeze(-1).tolist()):
                text = label["texts"][int(cls)]
                label["cls"][i] = text2id[tuple(text)]
            label["texts"] = mix_texts
        return labels

class Mosaic

class Mosaic(BaseMixTransform):
    """
    Mosaic augmentation.

    This class performs mosaic augmentation by combining multiple (4 or 9) images into a single mosaic image.
    The augmentation is applied to a dataset with a given probability.

    Attributes:
        dataset: The dataset on which the mosaic augmentation is applied.
        imgsz (int, optional): Image size (height and width) after mosaic pipeline of a single image. Default to 640.
        p (float, optional): Probability of applying the mosaic augmentation. Must be in the range 0-1. Default to 1.0.
        n (int, optional): The grid size, either 4 (for 2x2) or 9 (for 3x3).
    """

    def __init__(self, dataset, imgsz=640, p=1.0, n=4):
        """Initializes the object with a dataset, image size, probability, and border."""
        assert 0 <= p <= 1.0, f"The probability should be in range [0, 1], but got {p}."
        assert n in {4, 9}, "grid must be equal to 4 or 9."
        super().__init__(dataset=dataset, p=p)
        self.dataset = dataset
        self.imgsz = imgsz
        self.border = (-imgsz // 2, -imgsz // 2)  # width, height
        self.n = n

    def get_indexes(self, buffer=True):
        """Return a list of random indexes from the dataset."""
        if buffer:  # select images from buffer
            return random.choices(list(self.dataset.buffer), k=self.n - 1)
        else:  # select any images
            return [random.randint(0, len(self.dataset) - 1) for _ in range(self.n - 1)]

    def _mix_transform(self, labels):
        """Apply mixup transformation to the input image and labels."""
        assert labels.get("rect_shape", None) is None, "rect and mosaic are mutually exclusive."
        assert len(labels.get("mix_labels", [])), "There are no other images for mosaic augment."
        return (
            self._mosaic3(labels) if self.n == 3 else self._mosaic4(labels) if self.n == 4 else self._mosaic9(labels)
        )  # This code is modified for mosaic3 method.

    def _mosaic3(self, labels):
        """Create a 1x3 image mosaic."""
        mosaic_labels = []
        s = self.imgsz
        for i in range(3):
            labels_patch = labels if i == 0 else labels["mix_labels"][i - 1]
            # Load image
            img = labels_patch["img"]
            h, w = labels_patch.pop("resized_shape")

            # Place img in img3
            if i == 0:  # center
                img3 = np.full((s * 3, s * 3, img.shape[2]), 114, dtype=np.uint8)  # base image with 3 tiles
                h0, w0 = h, w
                c = s, s, s + w, s + h  # xmin, ymin, xmax, ymax (base) coordinates
            elif i == 1:  # right
                c = s + w0, s, s + w0 + w, s + h
            elif i == 2:  # left
                c = s - w, s + h0 - h, s, s + h0

            padw, padh = c[:2]
            x1, y1, x2, y2 = (max(x, 0) for x in c)  # allocate coords

            img3[y1:y2, x1:x2] = img[y1 - padh :, x1 - padw :]  # img3[ymin:ymax, xmin:xmax]
            # hp, wp = h, w  # height, width previous for next iteration

            # Labels assuming imgsz*2 mosaic size
            labels_patch = self._update_labels(labels_patch, padw + self.border[0], padh + self.border[1])
            mosaic_labels.append(labels_patch)
        final_labels = self._cat_labels(mosaic_labels)

        final_labels["img"] = img3[-self.border[0] : self.border[0], -self.border[1] : self.border[1]]
        return final_labels

    def _mosaic4(self, labels):
        """Create a 2x2 image mosaic."""
        mosaic_labels = []
        s = self.imgsz
        yc, xc = (int(random.uniform(-x, 2 * s + x)) for x in self.border)  # mosaic center x, y
        for i in range(4):
            labels_patch = labels if i == 0 else labels["mix_labels"][i - 1]
            # Load image
            img = labels_patch["img"]
            h, w = labels_patch.pop("resized_shape")

            # Place img in img4
            if i == 0:  # top left
                img4 = np.full((s * 2, s * 2, img.shape[2]), 114, dtype=np.uint8)  # base image with 4 tiles
                x1a, y1a, x2a, y2a = max(xc - w, 0), max(yc - h, 0), xc, yc  # xmin, ymin, xmax, ymax (large image)
                x1b, y1b, x2b, y2b = w - (x2a - x1a), h - (y2a - y1a), w, h  # xmin, ymin, xmax, ymax (small image)
            elif i == 1:  # top right
                x1a, y1a, x2a, y2a = xc, max(yc - h, 0), min(xc + w, s * 2), yc
                x1b, y1b, x2b, y2b = 0, h - (y2a - y1a), min(w, x2a - x1a), h
            elif i == 2:  # bottom left
                x1a, y1a, x2a, y2a = max(xc - w, 0), yc, xc, min(s * 2, yc + h)
                x1b, y1b, x2b, y2b = w - (x2a - x1a), 0, w, min(y2a - y1a, h)
            elif i == 3:  # bottom right
                x1a, y1a, x2a, y2a = xc, yc, min(xc + w, s * 2), min(s * 2, yc + h)
                x1b, y1b, x2b, y2b = 0, 0, min(w, x2a - x1a), min(y2a - y1a, h)

            img4[y1a:y2a, x1a:x2a] = img[y1b:y2b, x1b:x2b]  # img4[ymin:ymax, xmin:xmax]
            padw = x1a - x1b
            padh = y1a - y1b

            labels_patch = self._update_labels(labels_patch, padw, padh)
            mosaic_labels.append(labels_patch)
        final_labels = self._cat_labels(mosaic_labels)
        final_labels["img"] = img4
        return final_labels

    def _mosaic9(self, labels):
        """Create a 3x3 image mosaic."""
        mosaic_labels = []
        s = self.imgsz
        hp, wp = -1, -1  # height, width previous
        for i in range(9):
            labels_patch = labels if i == 0 else labels["mix_labels"][i - 1]
            # Load image
            img = labels_patch["img"]
            h, w = labels_patch.pop("resized_shape")

            # Place img in img9
            if i == 0:  # center
                img9 = np.full((s * 3, s * 3, img.shape[2]), 114, dtype=np.uint8)  # base image with 4 tiles
                h0, w0 = h, w
                c = s, s, s + w, s + h  # xmin, ymin, xmax, ymax (base) coordinates
            elif i == 1:  # top
                c = s, s - h, s + w, s
            elif i == 2:  # top right
                c = s + wp, s - h, s + wp + w, s
            elif i == 3:  # right
                c = s + w0, s, s + w0 + w, s + h
            elif i == 4:  # bottom right
                c = s + w0, s + hp, s + w0 + w, s + hp + h
            elif i == 5:  # bottom
                c = s + w0 - w, s + h0, s + w0, s + h0 + h
            elif i == 6:  # bottom left
                c = s + w0 - wp - w, s + h0, s + w0 - wp, s + h0 + h
            elif i == 7:  # left
                c = s - w, s + h0 - h, s, s + h0
            elif i == 8:  # top left
                c = s - w, s + h0 - hp - h, s, s + h0 - hp

            padw, padh = c[:2]
            x1, y1, x2, y2 = (max(x, 0) for x in c)  # allocate coords

            # Image
            img9[y1:y2, x1:x2] = img[y1 - padh :, x1 - padw :]  # img9[ymin:ymax, xmin:xmax]
            hp, wp = h, w  # height, width previous for next iteration

            # Labels assuming imgsz*2 mosaic size
            labels_patch = self._update_labels(labels_patch, padw + self.border[0], padh + self.border[1])
            mosaic_labels.append(labels_patch)
        final_labels = self._cat_labels(mosaic_labels)

        final_labels["img"] = img9[-self.border[0] : self.border[0], -self.border[1] : self.border[1]]
        return final_labels

    @staticmethod
    def _update_labels(labels, padw, padh):
        """Update labels."""
        nh, nw = labels["img"].shape[:2]
        labels["instances"].convert_bbox(format="xyxy")
        labels["instances"].denormalize(nw, nh)
        labels["instances"].add_padding(padw, padh)
        return labels

    def _cat_labels(self, mosaic_labels):
        """Return labels with mosaic border instances clipped."""
        if len(mosaic_labels) == 0:
            return {}
        cls = []
        instances = []
        imgsz = self.imgsz * 2  # mosaic imgsz
        for labels in mosaic_labels:
            cls.append(labels["cls"])
            instances.append(labels["instances"])
        # Final labels
        final_labels = {
            "im_file": mosaic_labels[0]["im_file"],
            "ori_shape": mosaic_labels[0]["ori_shape"],
            "resized_shape": (imgsz, imgsz),
            "cls": np.concatenate(cls, 0),
            "instances": Instances.concatenate(instances, axis=0),
            "mosaic_border": self.border,
        }
        final_labels["instances"].clip(imgsz, imgsz)
        good = final_labels["instances"].remove_zero_area_boxes()
        final_labels["cls"] = final_labels["cls"][good]
        if "texts" in mosaic_labels[0]:
            final_labels["texts"] = mosaic_labels[0]["texts"]
        return final_labels

具体介绍一下_mosaic3

静态方法更新label

    # 静态方法，用于更新单个图像的标签
    @staticmethod
    def _update_labels(labels, padw, padh):
        # 获取图像的高度和宽度
        nh, nw = labels["img"].shape[:2]

        # 将实例（boxes）转换为xyxy格式
        labels["instances"].convert_bbox(format="xyxy")

        # 反标准化实例坐标，基于图像的实际尺寸
        labels["instances"].denormalize(nw, nh)

        # 添加填充到实例坐标
        labels["instances"].add_padding(padw, padh)

        # 返回更新后的标签
        return labels

    # 静态方法，用于将多个图像的标签组合成一个拼贴图像的标签
    @staticmethod
    def _cat_labels(mosaic_labels):
        # 检查输入列表是否为空
        if len(mosaic_labels) == 0:
            return {}

        # 初始化类别列表和实例列表
        cls = []
        instances = []

        # 拼贴图像的大小是原始图像大小的两倍
        imgsz = self.imgsz * 2

        # 遍历每个图像的标签
        for labels in mosaic_labels:
            # 收集类别
            cls.append(labels["cls"])
            # 收集实例
            instances.append(labels["instances"])

        # 创建最终的标签字典
        final_labels = {
            "im_file": mosaic_labels[0]["im_file"],  # 图像的文件名
            "ori_shape": mosaic_labels[0]["ori_shape"],  # 图像的原始形状
            "resized_shape": (imgsz, imgsz),  # 拼贴图像的尺寸
            "cls": np.concatenate(cls, 0),  # 合并所有图像的类别
            "instances": Instances.concatenate(instances, axis=0),  # 合并所有图像的实例
            "mosaic_border": self.border,  # 拼贴图像的边框信息
        }

        # 裁剪超出拼贴图像边界的实例
        final_labels["instances"].clip(imgsz, imgsz)

        # 移除面积为零的实例
        good = final_labels["instances"].remove_zero_area_boxes()

        # 根据有效的实例更新类别
        final_labels["cls"] = final_labels["cls"][good]

        # 如果原始标签中有"texts"字段，将其添加到最终标签中
        if "texts" in mosaic_labels[0]:
            final_labels["texts"] = mosaic_labels[0]["texts"]

        # 返回组合后的标签
        return final_labels

class MixUp

class MixUp(BaseMixTransform):
    """Class for applying MixUp augmentation to the dataset."""

    def __init__(self, dataset, pre_transform=None, p=0.0) -> None:
        """初始化MixUp对象，传入数据集、预处理变换和应用MixUp的概率。

        参数:
        - dataset: 数据集对象
        - pre_transform: 可选的预处理变换
        - p: 应用MixUp的概率，默认为0.0，表示默认不应用MixUp
        """
        super().__init__(dataset=dataset, pre_transform=pre_transform, p=p)

    def get_indexes(self):
        """从数据集中随机获取一个索引。

        返回:
        - 一个随机生成的整数索引，范围在0到数据集长度减1之间。
        """
        return random.randint(0, len(self.dataset) - 1)

    def _mix_transform(self, labels):
        """根据https://arxiv.org/pdf/1710.09412.pdf中的描述应用MixUp数据增强。

        参数:
        - labels: 包含图像和对应标签的字典，如{'img': 图像, 'instances': 实例, 'cls': 类别}

        返回:
        - 应用MixUp后的混合标签字典。
        """
        # 生成MixUp的混合比例，这里使用alpha=beta=32.0
        r = np.random.beta(32.0, 32.0)

        # 获取第二个图像及其标签
        labels2 = labels["mix_labels"][0]

        # 混合两个图像
        mixed_img = (labels["img"] * r + labels2["img"] * (1 - r)).astype(np.uint8)

        # 混合两个实例（如边界框）
        mixed_instances = Instances.concatenate([labels["instances"], labels2["instances"]], axis=0)

        # 混合两个类别
        mixed_cls = np.concatenate([labels["cls"], labels2["cls"]], 0)

        # 返回混合后的标签字典
        return {"img": mixed_img, "instances": mixed_instances, "cls": mixed_cls}

RandomPerspective

class RandomPerspective:
    """
    Implements random perspective and affine transformations on images and corresponding bounding boxes, segments, and
    keypoints. These transformations include rotation, translation, scaling, and shearing. The class also offers the
    option to apply these transformations conditionally with a specified probability.

    Attributes:
        degrees (float): Degree range for random rotations.
        translate (float): Fraction of total width and height for random translation.
        scale (float): Scaling factor interval, e.g., a scale factor of 0.1 allows a resize between 90%-110%.
        shear (float): Shear intensity (angle in degrees).
        perspective (float): Perspective distortion factor.
        border (tuple): Tuple specifying mosaic border.
        pre_transform (callable): A function/transform to apply to the image before starting the random transformation.

    Methods:
        affine_transform(img, border): Applies a series of affine transformations to the image.
        apply_bboxes(bboxes, M): Transforms bounding boxes using the calculated affine matrix.
        apply_segments(segments, M): Transforms segments and generates new bounding boxes.
        apply_keypoints(keypoints, M): Transforms keypoints.
        __call__(labels): Main method to apply transformations to both images and their corresponding annotations.
        box_candidates(box1, box2): Filters out bounding boxes that don't meet certain criteria post-transformation.
    """

    def __init__(
        self, degrees=0.0, translate=0.1, scale=0.5, shear=0.0, perspective=0.0, border=(0, 0), pre_transform=None
    ):
        """Initializes RandomPerspective object with transformation parameters."""

        self.degrees = degrees
        self.translate = translate
        self.scale = scale
        self.shear = shear
        self.perspective = perspective
        self.border = border  # mosaic border
        self.pre_transform = pre_transform

    def affine_transform(self, img, border):
        """
        Applies a sequence of affine transformations centered around the image center.

        Args:
            img (ndarray): Input image.
            border (tuple): Border dimensions.

        Returns:
            img (ndarray): Transformed image.
            M (ndarray): Transformation matrix.
            s (float): Scale factor.
        """

        # Center
        C = np.eye(3, dtype=np.float32)

        C[0, 2] = -img.shape[1] / 2  # x translation (pixels)
        C[1, 2] = -img.shape[0] / 2  # y translation (pixels)

        # Perspective
        P = np.eye(3, dtype=np.float32)
        P[2, 0] = random.uniform(-self.perspective, self.perspective)  # x perspective (about y)
        P[2, 1] = random.uniform(-self.perspective, self.perspective)  # y perspective (about x)

        # Rotation and Scale
        R = np.eye(3, dtype=np.float32)
        a = random.uniform(-self.degrees, self.degrees)
        # a += random.choice([-180, -90, 0, 90])  # add 90deg rotations to small rotations
        s = random.uniform(1 - self.scale, 1 + self.scale)
        # s = 2 ** random.uniform(-scale, scale)
        R[:2] = cv2.getRotationMatrix2D(angle=a, center=(0, 0), scale=s)

        # Shear
        S = np.eye(3, dtype=np.float32)
        S[0, 1] = math.tan(random.uniform(-self.shear, self.shear) * math.pi / 180)  # x shear (deg)
        S[1, 0] = math.tan(random.uniform(-self.shear, self.shear) * math.pi / 180)  # y shear (deg)

        # Translation
        T = np.eye(3, dtype=np.float32)
        T[0, 2] = random.uniform(0.5 - self.translate, 0.5 + self.translate) * self.size[0]  # x translation (pixels)
        T[1, 2] = random.uniform(0.5 - self.translate, 0.5 + self.translate) * self.size[1]  # y translation (pixels)

        # Combined rotation matrix
        M = T @ S @ R @ P @ C  # order of operations (right to left) is IMPORTANT
        # Affine image
        if (border[0] != 0) or (border[1] != 0) or (M != np.eye(3)).any():  # image changed
            if self.perspective:
                img = cv2.warpPerspective(img, M, dsize=self.size, borderValue=(114, 114, 114))
            else:  # affine
                img = cv2.warpAffine(img, M[:2], dsize=self.size, borderValue=(114, 114, 114))
        return img, M, s

    def apply_bboxes(self, bboxes, M):
        """
        Apply affine to bboxes only.

        Args:
            bboxes (ndarray): list of bboxes, xyxy format, with shape (num_bboxes, 4).
            M (ndarray): affine matrix.

        Returns:
            new_bboxes (ndarray): bboxes after affine, [num_bboxes, 4].
        """
        n = len(bboxes)
        if n == 0:
            return bboxes

        xy = np.ones((n * 4, 3), dtype=bboxes.dtype)
        xy[:, :2] = bboxes[:, [0, 1, 2, 3, 0, 3, 2, 1]].reshape(n * 4, 2)  # x1y1, x2y2, x1y2, x2y1
        xy = xy @ M.T  # transform
        xy = (xy[:, :2] / xy[:, 2:3] if self.perspective else xy[:, :2]).reshape(n, 8)  # perspective rescale or affine

        # Create new boxes
        x = xy[:, [0, 2, 4, 6]]
        y = xy[:, [1, 3, 5, 7]]
        return np.concatenate((x.min(1), y.min(1), x.max(1), y.max(1)), dtype=bboxes.dtype).reshape(4, n).T

    def apply_segments(self, segments, M):
        """
        Apply affine to segments and generate new bboxes from segments.

        Args:
            segments (ndarray): list of segments, [num_samples, 500, 2].
            M (ndarray): affine matrix.

        Returns:
            new_segments (ndarray): list of segments after affine, [num_samples, 500, 2].
            new_bboxes (ndarray): bboxes after affine, [N, 4].
        """
        n, num = segments.shape[:2]
        if n == 0:
            return [], segments

        xy = np.ones((n * num, 3), dtype=segments.dtype)
        segments = segments.reshape(-1, 2)
        xy[:, :2] = segments
        xy = xy @ M.T  # transform
        xy = xy[:, :2] / xy[:, 2:3]
        segments = xy.reshape(n, -1, 2)
        bboxes = np.stack([segment2box(xy, self.size[0], self.size[1]) for xy in segments], 0)
        segments[..., 0] = segments[..., 0].clip(bboxes[:, 0:1], bboxes[:, 2:3])
        segments[..., 1] = segments[..., 1].clip(bboxes[:, 1:2], bboxes[:, 3:4])
        return bboxes, segments

    def apply_keypoints(self, keypoints, M):
        """
        Apply affine to keypoints.

        Args:
            keypoints (ndarray): keypoints, [N, 17, 3].
            M (ndarray): affine matrix.

        Returns:
            new_keypoints (ndarray): keypoints after affine, [N, 17, 3].
        """
        n, nkpt = keypoints.shape[:2]
        if n == 0:
            return keypoints
        xy = np.ones((n * nkpt, 3), dtype=keypoints.dtype)
        visible = keypoints[..., 2].reshape(n * nkpt, 1)
        xy[:, :2] = keypoints[..., :2].reshape(n * nkpt, 2)
        xy = xy @ M.T  # transform
        xy = xy[:, :2] / xy[:, 2:3]  # perspective rescale or affine
        out_mask = (xy[:, 0] < 0) | (xy[:, 1] < 0) | (xy[:, 0] > self.size[0]) | (xy[:, 1] > self.size[1])
        visible[out_mask] = 0
        return np.concatenate([xy, visible], axis=-1).reshape(n, nkpt, 3)

    def __call__(self, labels):
        """
        Affine images and targets.

        Args:
            labels (dict): a dict of `bboxes`, `segments`, `keypoints`.
        """
        if self.pre_transform and "mosaic_border" not in labels:
            labels = self.pre_transform(labels)
        labels.pop("ratio_pad", None)  # do not need ratio pad

        img = labels["img"]
        cls = labels["cls"]
        instances = labels.pop("instances")
        # Make sure the coord formats are right
        instances.convert_bbox(format="xyxy")
        instances.denormalize(*img.shape[:2][::-1])

        border = labels.pop("mosaic_border", self.border)
        self.size = img.shape[1] + border[1] * 2, img.shape[0] + border[0] * 2  # w, h
        # M is affine matrix
        # Scale for func:`box_candidates`
        img, M, scale = self.affine_transform(img, border)

        bboxes = self.apply_bboxes(instances.bboxes, M)

        segments = instances.segments
        keypoints = instances.keypoints
        # Update bboxes if there are segments.
        if len(segments):
            bboxes, segments = self.apply_segments(segments, M)

        if keypoints is not None:
            keypoints = self.apply_keypoints(keypoints, M)
        new_instances = Instances(bboxes, segments, keypoints, bbox_format="xyxy", normalized=False)
        # Clip
        new_instances.clip(*self.size)

        # Filter instances
        instances.scale(scale_w=scale, scale_h=scale, bbox_only=True)
        # Make the bboxes have the same scale with new_bboxes
        i = self.box_candidates(
            box1=instances.bboxes.T, box2=new_instances.bboxes.T, area_thr=0.01 if len(segments) else 0.10
        )
        labels["instances"] = new_instances[i]
        labels["cls"] = cls[i]
        labels["img"] = img
        labels["resized_shape"] = img.shape[:2]
        return labels

    def box_candidates(self, box1, box2, wh_thr=2, ar_thr=100, area_thr=0.1, eps=1e-16):
        """
        Compute box candidates based on a set of thresholds. This method compares the characteristics of the boxes
        before and after augmentation to decide whether a box is a candidate for further processing.

        Args:
            box1 (numpy.ndarray): The 4,n bounding box before augmentation, represented as [x1, y1, x2, y2].
            box2 (numpy.ndarray): The 4,n bounding box after augmentation, represented as [x1, y1, x2, y2].
            wh_thr (float, optional): The width and height threshold in pixels. Default is 2.
            ar_thr (float, optional): The aspect ratio threshold. Default is 100.
            area_thr (float, optional): The area ratio threshold. Default is 0.1.
            eps (float, optional): A small epsilon value to prevent division by zero. Default is 1e-16.

        Returns:
            (numpy.ndarray): A boolean array indicating which boxes are candidates based on the given thresholds.
        """
        w1, h1 = box1[2] - box1[0], box1[3] - box1[1]
        w2, h2 = box2[2] - box2[0], box2[3] - box2[1]
        ar = np.maximum(w2 / (h2 + eps), h2 / (w2 + eps))  # aspect ratio
        return (w2 > wh_thr) & (h2 > wh_thr) & (w2 * h2 / (w1 * h1 + eps) > area_thr) & (ar < ar_thr)  # candidates

M = T @ S @ R @ P @ C

关于这种矩阵变换可以看下面这个网址：
矩阵变换

class RandomHSV

class RandomHSV:
    """
    This class is responsible for performing random adjustments to the Hue, Saturation, and Value (HSV) channels of an
    image.

    The adjustments are random but within limits set by hgain, sgain, and vgain.
    """

    def __init__(self, hgain=0.5, sgain=0.5, vgain=0.5) -> None:
        """
        Initialize RandomHSV class with gains for each HSV channel.

        Args:
            hgain (float, optional): Maximum variation for hue. Default is 0.5.
            sgain (float, optional): Maximum variation for saturation. Default is 0.5.
            vgain (float, optional): Maximum variation for value. Default is 0.5.
        """
        self.hgain = hgain
        self.sgain = sgain
        self.vgain = vgain

    def __call__(self, labels):
        """
        Applies random HSV augmentation to an image within the predefined limits.

        The modified image replaces the original image in the input 'labels' dict.
        """
        img = labels["img"]
        if self.hgain or self.sgain or self.vgain:
            r = np.random.uniform(-1, 1, 3) * [self.hgain, self.sgain, self.vgain] + 1  # random gains
            hue, sat, val = cv2.split(cv2.cvtColor(img, cv2.COLOR_BGR2HSV))
            dtype = img.dtype  # uint8

            x = np.arange(0, 256, dtype=r.dtype)
            lut_hue = ((x * r[0]) % 180).astype(dtype)
            lut_sat = np.clip(x * r[1], 0, 255).astype(dtype)
            lut_val = np.clip(x * r[2], 0, 255).astype(dtype)

            im_hsv = cv2.merge((cv2.LUT(hue, lut_hue), cv2.LUT(sat, lut_sat), cv2.LUT(val, lut_val)))
            cv2.cvtColor(im_hsv, cv2.COLOR_HSV2BGR, dst=img)  # no return needed
        return labels

class RandomFlip

class RandomFlip:
    """
    Applies a random horizontal or vertical flip to an image with a given probability.

    Also updates any instances (bounding boxes, keypoints, etc.) accordingly.
    """

    def __init__(self, p=0.5, direction="horizontal", flip_idx=None) -> None:
        """
        Initializes the RandomFlip class with probability and direction.

        Args:
            p (float, optional): The probability of applying the flip. Must be between 0 and 1. Default is 0.5.
            direction (str, optional): The direction to apply the flip. Must be 'horizontal' or 'vertical'.
                Default is 'horizontal'.
            flip_idx (array-like, optional): Index mapping for flipping keypoints, if any.
        """
        assert direction in {"horizontal", "vertical"}, f"Support direction `horizontal` or `vertical`, got {direction}"
        assert 0 <= p <= 1.0

        self.p = p
        self.direction = direction
        self.flip_idx = flip_idx

    def __call__(self, labels):
        """
        Applies random flip to an image and updates any instances like bounding boxes or keypoints accordingly.

        Args:
            labels (dict): A dictionary containing the keys 'img' and 'instances'. 'img' is the image to be flipped.
                           'instances' is an object containing bounding boxes and optionally keypoints.

        Returns:
            (dict): The same dict with the flipped image and updated instances under the 'img' and 'instances' keys.
        """
        img = labels["img"]
        instances = labels.pop("instances")
        instances.convert_bbox(format="xywh")
        h, w = img.shape[:2]
        h = 1 if instances.normalized else h
        w = 1 if instances.normalized else w

        # Flip up-down
        if self.direction == "vertical" and random.random() < self.p:
            img = np.flipud(img)
            instances.flipud(h)
        if self.direction == "horizontal" and random.random() < self.p:
            img = np.fliplr(img)
            instances.fliplr(w)
            # For keypoints
            if self.flip_idx is not None and instances.keypoints is not None:
                instances.keypoints = np.ascontiguousarray(instances.keypoints[:, self.flip_idx, :])
        labels["img"] = np.ascontiguousarray(img)
        labels["instances"] = instances
        return labels

class LetterBox

class LetterBox:
    """Resize image and padding for detection, instance segmentation, pose."""

    def __init__(self, new_shape=(640, 640), auto=False, scaleFill=False, scaleup=True, center=True, stride=32):
        """Initialize LetterBox object with specific parameters."""
        self.new_shape = new_shape
        self.auto = auto
        self.scaleFill = scaleFill
        self.scaleup = scaleup
        self.stride = stride
        self.center = center  # Put the image in the middle or top-left

    def __call__(self, labels=None, image=None):
        """Return updated labels and image with added border."""
        if labels is None:
            labels = {}
        img = labels.get("img") if image is None else image
        shape = img.shape[:2]  # current shape [height, width]
        new_shape = labels.pop("rect_shape", self.new_shape)
        if isinstance(new_shape, int):
            new_shape = (new_shape, new_shape)

        # Scale ratio (new / old)
        r = min(new_shape[0] / shape[0], new_shape[1] / shape[1])
        if not self.scaleup:  # only scale down, do not scale up (for better val mAP)
            r = min(r, 1.0)

        # Compute padding
        ratio = r, r  # width, height ratios
        new_unpad = int(round(shape[1] * r)), int(round(shape[0] * r))
        dw, dh = new_shape[1] - new_unpad[0], new_shape[0] - new_unpad[1]  # wh padding
        if self.auto:  # minimum rectangle
            dw, dh = np.mod(dw, self.stride), np.mod(dh, self.stride)  # wh padding
        elif self.scaleFill:  # stretch
            dw, dh = 0.0, 0.0
            new_unpad = (new_shape[1], new_shape[0])
            ratio = new_shape[1] / shape[1], new_shape[0] / shape[0]  # width, height ratios

        if self.center:
            dw /= 2  # divide padding into 2 sides
            dh /= 2

        if shape[::-1] != new_unpad:  # resize
            img = cv2.resize(img, new_unpad, interpolation=cv2.INTER_LINEAR)
        top, bottom = int(round(dh - 0.1)) if self.center else 0, int(round(dh + 0.1))
        left, right = int(round(dw - 0.1)) if self.center else 0, int(round(dw + 0.1))
        img = cv2.copyMakeBorder(
            img, top, bottom, left, right, cv2.BORDER_CONSTANT, value=(114, 114, 114)
        )  # add border
        if labels.get("ratio_pad"):
            labels["ratio_pad"] = (labels["ratio_pad"], (left, top))  # for evaluation

        if len(labels):
            labels = self._update_labels(labels, ratio, dw, dh)
            labels["img"] = img
            labels["resized_shape"] = new_shape
            return labels
        else:
            return img

    def _update_labels(self, labels, ratio, padw, padh):
        """Update labels."""
        labels["instances"].convert_bbox(format="xyxy")
        labels["instances"].denormalize(*labels["img"].shape[:2][::-1])
        labels["instances"].scale(*ratio)
        labels["instances"].add_padding(padw, padh)
        return labels

class CopyPaste

class CopyPaste:
    """
    Implements the Copy-Paste augmentation as described in the paper https://arxiv.org/abs/2012.07177. This class is
    responsible for applying the Copy-Paste augmentation on images and their corresponding instances.
    """

    def __init__(self, p=0.5) -> None:
        """
        Initializes the CopyPaste class with a given probability.

        Args:
            p (float, optional): The probability of applying the Copy-Paste augmentation. Must be between 0 and 1.
                                 Default is 0.5.
        """
        self.p = p

    def __call__(self, labels):
        """
        Applies the Copy-Paste augmentation to the given image and instances.

        Args:
            labels (dict): A dictionary containing:
                           - 'img': The image to augment.
                           - 'cls': Class labels associated with the instances.
                           - 'instances': Object containing bounding boxes, and optionally, keypoints and segments.

        Returns:
            (dict): Dict with augmented image and updated instances under the 'img', 'cls', and 'instances' keys.

        Notes:
            1. Instances are expected to have 'segments' as one of their attributes for this augmentation to work.
            2. This method modifies the input dictionary 'labels' in place.
        """
        im = labels["img"]
        cls = labels["cls"]
        h, w = im.shape[:2]
        instances = labels.pop("instances")
        instances.convert_bbox(format="xyxy")
        instances.denormalize(w, h)
        if self.p and len(instances.segments):
            n = len(instances)
            _, w, _ = im.shape  # height, width, channels
            im_new = np.zeros(im.shape, np.uint8)

            # Calculate ioa first then select indexes randomly
            ins_flip = deepcopy(instances)
            ins_flip.fliplr(w)

            ioa = bbox_ioa(ins_flip.bboxes, instances.bboxes)  # intersection over area, (N, M)
            indexes = np.nonzero((ioa < 0.30).all(1))[0]  # (N, )
            n = len(indexes)
            for j in random.sample(list(indexes), k=round(self.p * n)):
                cls = np.concatenate((cls, cls[[j]]), axis=0)
                instances = Instances.concatenate((instances, ins_flip[[j]]), axis=0)
                cv2.drawContours(im_new, instances.segments[[j]].astype(np.int32), -1, (1, 1, 1), cv2.FILLED)

            result = cv2.flip(im, 1)  # augment segments (flip left-right)
            i = cv2.flip(im_new, 1).astype(bool)
            im[i] = result[i]

        labels["img"] = im
        labels["cls"] = cls
        labels["instances"] = instances
        return labels

class Albumtation

class Albumentations:
    """
    Albumentations transformations.

    Optional, uninstall package to disable. Applies Blur, Median Blur, convert to grayscale, Contrast Limited Adaptive
    Histogram Equalization, random change of brightness and contrast, RandomGamma and lowering of image quality by
    compression.
    """

    def __init__(self, p=1.0):
        """Initialize the transform object for YOLO bbox formatted params."""
        self.p = p
        self.transform = None
        prefix = colorstr("albumentations: ")
        try:
            import albumentations as A

            check_version(A.__version__, "1.0.3", hard=True)  # version requirement

            # Transforms
            T = [
                A.Blur(p=0.01),
                A.MedianBlur(p=0.01),
                A.ToGray(p=0.01),
                A.CLAHE(p=0.01),
                A.RandomBrightnessContrast(p=0.0),
                A.RandomGamma(p=0.0),
                A.ImageCompression(quality_lower=75, p=0.0),
            ]
            self.transform = A.Compose(T, bbox_params=A.BboxParams(format="yolo", label_fields=["class_labels"]))

            LOGGER.info(prefix + ", ".join(f"{x}".replace("always_apply=False, ", "") for x in T if x.p))
        except ImportError:  # package not installed, skip
            pass
        except Exception as e:
            LOGGER.info(f"{prefix}{e}")

    def __call__(self, labels):
        """Generates object detections and returns a dictionary with detection results."""
        im = labels["img"]
        cls = labels["cls"]
        if len(cls):
            labels["instances"].convert_bbox("xywh")
            labels["instances"].normalize(*im.shape[:2][::-1])
            bboxes = labels["instances"].bboxes
            # TODO: add supports of segments and keypoints
            if self.transform and random.random() < self.p:
                new = self.transform(image=im, bboxes=bboxes, class_labels=cls)  # transformed
                if len(new["class_labels"]) > 0:  # skip update if no bbox in new im
                    labels["img"] = new["image"]
                    labels["cls"] = np.array(new["class_labels"])
                    bboxes = np.array(new["bboxes"], dtype=np.float32)
            labels["instances"].update(bboxes=bboxes)
        return labels

class Format

class Format:
    """
    Formats image annotations for object detection, instance segmentation, and pose estimation tasks. The class
    standardizes the image and instance annotations to be used by the `collate_fn` in PyTorch DataLoader.

    Attributes:
        bbox_format (str): Format for bounding boxes. Default is 'xywh'.
        normalize (bool): Whether to normalize bounding boxes. Default is True.
        return_mask (bool): Return instance masks for segmentation. Default is False.
        return_keypoint (bool): Return keypoints for pose estimation. Default is False.
        mask_ratio (int): Downsample ratio for masks. Default is 4.
        mask_overlap (bool): Whether to overlap masks. Default is True.
        batch_idx (bool): Keep batch indexes. Default is True.
        bgr (float): The probability to return BGR images. Default is 0.0.
    """

    def __init__(
        self,
        bbox_format="xywh",
        normalize=True,
        return_mask=False,
        return_keypoint=False,
        return_obb=False,
        mask_ratio=4,
        mask_overlap=True,
        batch_idx=True,
        bgr=0.0,
    ):
        """Initializes the Format class with given parameters."""
        self.bbox_format = bbox_format
        self.normalize = normalize
        self.return_mask = return_mask  # set False when training detection only
        self.return_keypoint = return_keypoint
        self.return_obb = return_obb
        self.mask_ratio = mask_ratio
        self.mask_overlap = mask_overlap
        self.batch_idx = batch_idx  # keep the batch indexes
        self.bgr = bgr

    def __call__(self, labels):
        """Return formatted image, classes, bounding boxes & keypoints to be used by 'collate_fn'."""
        img = labels.pop("img")
        h, w = img.shape[:2]
        cls = labels.pop("cls")
        instances = labels.pop("instances")
        instances.convert_bbox(format=self.bbox_format)
        instances.denormalize(w, h)
        nl = len(instances)

        if self.return_mask:
            if nl:
                masks, instances, cls = self._format_segments(instances, cls, w, h)
                masks = torch.from_numpy(masks)
            else:
                masks = torch.zeros(
                    1 if self.mask_overlap else nl, img.shape[0] // self.mask_ratio, img.shape[1] // self.mask_ratio
                )
            labels["masks"] = masks
        labels["img"] = self._format_img(img)
        labels["cls"] = torch.from_numpy(cls) if nl else torch.zeros(nl)
        labels["bboxes"] = torch.from_numpy(instances.bboxes) if nl else torch.zeros((nl, 4))
        if self.return_keypoint:
            labels["keypoints"] = torch.from_numpy(instances.keypoints)
            if self.normalize:
                labels["keypoints"][..., 0] /= w
                labels["keypoints"][..., 1] /= h
        if self.return_obb:
            labels["bboxes"] = (
                xyxyxyxy2xywhr(torch.from_numpy(instances.segments)) if len(instances.segments) else torch.zeros((0, 5))
            )
        # NOTE: need to normalize obb in xywhr format for width-height consistency
        if self.normalize:
            labels["bboxes"][:, [0, 2]] /= w
            labels["bboxes"][:, [1, 3]] /= h
        # Then we can use collate_fn
        if self.batch_idx:
            labels["batch_idx"] = torch.zeros(nl)
        return labels

    def _format_img(self, img):
        """Format the image for YOLO from Numpy array to PyTorch tensor."""
        if len(img.shape) < 3:
            img = np.expand_dims(img, -1)
        img = img.transpose(2, 0, 1)
        img = np.ascontiguousarray(img[::-1] if random.uniform(0, 1) > self.bgr else img)
        img = torch.from_numpy(img)
        return img

    def _format_segments(self, instances, cls, w, h):
        """Convert polygon points to bitmap."""
        segments = instances.segments
        if self.mask_overlap:
            masks, sorted_idx = polygons2masks_overlap((h, w), segments, downsample_ratio=self.mask_ratio)
            masks = masks[None]  # (640, 640) -> (1, 640, 640)
            instances = instances[sorted_idx]
            cls = cls[sorted_idx]
        else:
            masks = polygons2masks((h, w), segments, color=1, downsample_ratio=self.mask_ratio)

        return masks, instances, cls

class

class RandomLoadText:
    """
    Randomly sample positive texts and negative texts and update the class indices accordingly to the number of samples.

    Attributes:
        prompt_format (str): Format for prompt. Default is '{}'.
        neg_samples (tuple[int]): A ranger to randomly sample negative texts, Default is (80, 80).
        max_samples (int): The max number of different text samples in one image, Default is 80.
        padding (bool): Whether to pad texts to max_samples. Default is False.
        padding_value (str): The padding text. Default is "".
    """

    def __init__(
        self,
        prompt_format: str = "{}",
        neg_samples: Tuple[int, int] = (80, 80),
        max_samples: int = 80,
        padding: bool = False,
        padding_value: str = "",
    ) -> None:
        """Initializes the RandomLoadText class with given parameters."""
        self.prompt_format = prompt_format
        self.neg_samples = neg_samples
        self.max_samples = max_samples
        self.padding = padding
        self.padding_value = padding_value

    def __call__(self, labels: dict) -> dict:
        """Return updated classes and texts."""
        assert "texts" in labels, "No texts found in labels."
        class_texts = labels["texts"]
        num_classes = len(class_texts)
        cls = np.asarray(labels.pop("cls"), dtype=int)
        pos_labels = np.unique(cls).tolist()

        if len(pos_labels) > self.max_samples:
            pos_labels = set(random.sample(pos_labels, k=self.max_samples))

        neg_samples = min(min(num_classes, self.max_samples) - len(pos_labels), random.randint(*self.neg_samples))
        neg_labels = []
        for i in range(num_classes):
            if i not in pos_labels:
                neg_labels.append(i)
        neg_labels = random.sample(neg_labels, k=neg_samples)

        sampled_labels = pos_labels + neg_labels
        random.shuffle(sampled_labels)

        label2ids = {label: i for i, label in enumerate(sampled_labels)}
        valid_idx = np.zeros(len(labels["instances"]), dtype=bool)
        new_cls = []
        for i, label in enumerate(cls.squeeze(-1).tolist()):
            if label not in label2ids:
                continue
            valid_idx[i] = True
            new_cls.append([label2ids[label]])
        labels["instances"] = labels["instances"][valid_idx]
        labels["cls"] = np.array(new_cls)

        # Randomly select one prompt when there's more than one prompts
        texts = []
        for label in sampled_labels:
            prompts = class_texts[label]
            assert len(prompts) > 0
            prompt = self.prompt_format.format(prompts[random.randrange(len(prompts))])
            texts.append(prompt)

        if self.padding:
            valid_labels = len(pos_labels) + len(neg_labels)
            num_padding = self.max_samples - valid_labels
            if num_padding > 0:
                texts += [self.padding_value] * num_padding

        labels["texts"] = texts
        return labels

v8_transforms

def v8_transforms(dataset, imgsz, hyp, stretch=False):
    """Convert images to a size suitable for YOLOv8 training."""
    pre_transform = Compose(
        [
            Mosaic(dataset, imgsz=imgsz, p=hyp.mosaic),
            CopyPaste(p=hyp.copy_paste),
            RandomPerspective(
                degrees=hyp.degrees,
                translate=hyp.translate,
                scale=hyp.scale,
                shear=hyp.shear,
                perspective=hyp.perspective,
                pre_transform=None if stretch else LetterBox(new_shape=(imgsz, imgsz)),
            ),
        ]
    )
    flip_idx = dataset.data.get("flip_idx", [])  # for keypoints augmentation
    if dataset.use_keypoints:
        kpt_shape = dataset.data.get("kpt_shape", None)
        if len(flip_idx) == 0 and hyp.fliplr > 0.0:
            hyp.fliplr = 0.0
            LOGGER.warning("WARNING ⚠️ No 'flip_idx' array defined in data.yaml, setting augmentation 'fliplr=0.0'")
        elif flip_idx and (len(flip_idx) != kpt_shape[0]):
            raise ValueError(f"data.yaml flip_idx={flip_idx} length must be equal to kpt_shape[0]={kpt_shape[0]}")

    return Compose(
        [
            pre_transform,
            MixUp(dataset, pre_transform=pre_transform, p=hyp.mixup),
            Albumentations(p=1.0),
            RandomHSV(hgain=hyp.hsv_h, sgain=hyp.hsv_s, vgain=hyp.hsv_v),
            RandomFlip(direction="vertical", p=hyp.flipud),
            RandomFlip(direction="horizontal", p=hyp.fliplr, flip_idx=flip_idx),
        ]
    )  # transforms

classify_transforms

# Classification augmentations -----------------------------------------------------------------------------------------
def classify_transforms(
    size=224,
    mean=DEFAULT_MEAN,
    std=DEFAULT_STD,
    interpolation=Image.BILINEAR,
    crop_fraction: float = DEFAULT_CROP_FRACTION,
):
    """
    Classification transforms for evaluation/inference. Inspired by timm/data/transforms_factory.py.

    Args:
        size (int): image size
        mean (tuple): mean values of RGB channels
        std (tuple): std values of RGB channels
        interpolation (T.InterpolationMode): interpolation mode. default is T.InterpolationMode.BILINEAR.
        crop_fraction (float): fraction of image to crop. default is 1.0.

    Returns:
        (T.Compose): torchvision transforms
    """
    import torchvision.transforms as T  # scope for faster 'import ultralytics'

    if isinstance(size, (tuple, list)):
        assert len(size) == 2
        scale_size = tuple(math.floor(x / crop_fraction) for x in size)
    else:
        scale_size = math.floor(size / crop_fraction)
        scale_size = (scale_size, scale_size)

    # Aspect ratio is preserved, crops center within image, no borders are added, image is lost
    if scale_size[0] == scale_size[1]:
        # Simple case, use torchvision built-in Resize with the shortest edge mode (scalar size arg)
        tfl = [T.Resize(scale_size[0], interpolation=interpolation)]
    else:
        # Resize the shortest edge to matching target dim for non-square target
        tfl = [T.Resize(scale_size)]
    tfl += [T.CenterCrop(size)]

    tfl += [
        T.ToTensor(),
        T.Normalize(
            mean=torch.tensor(mean),
            std=torch.tensor(std),
        ),
    ]

    return T.Compose(tfl)

# Classification training augmentations --------------------------------------------------------------------------------
def classify_augmentations(
    size=224,
    mean=DEFAULT_MEAN,
    std=DEFAULT_STD,
    scale=None,
    ratio=None,
    hflip=0.5,
    vflip=0.0,
    auto_augment=None,
    hsv_h=0.015,  # image HSV-Hue augmentation (fraction)
    hsv_s=0.4,  # image HSV-Saturation augmentation (fraction)
    hsv_v=0.4,  # image HSV-Value augmentation (fraction)
    force_color_jitter=False,
    erasing=0.0,
    interpolation=Image.BILINEAR,
):
    """
    Classification transforms with augmentation for training. Inspired by timm/data/transforms_factory.py.

    Args:
        size (int): image size
        scale (tuple): scale range of the image. default is (0.08, 1.0)
        ratio (tuple): aspect ratio range of the image. default is (3./4., 4./3.)
        mean (tuple): mean values of RGB channels
        std (tuple): std values of RGB channels
        hflip (float): probability of horizontal flip
        vflip (float): probability of vertical flip
        auto_augment (str): auto augmentation policy. can be 'randaugment', 'augmix', 'autoaugment' or None.
        hsv_h (float): image HSV-Hue augmentation (fraction)
        hsv_s (float): image HSV-Saturation augmentation (fraction)
        hsv_v (float): image HSV-Value augmentation (fraction)
        force_color_jitter (bool): force to apply color jitter even if auto augment is enabled
        erasing (float): probability of random erasing
        interpolation (T.InterpolationMode): interpolation mode. default is T.InterpolationMode.BILINEAR.

    Returns:
        (T.Compose): torchvision transforms
    """
    # Transforms to apply if Albumentations not installed
    import torchvision.transforms as T  # scope for faster 'import ultralytics'

    if not isinstance(size, int):
        raise TypeError(f"classify_transforms() size {size} must be integer, not (list, tuple)")
    scale = tuple(scale or (0.08, 1.0))  # default imagenet scale range
    ratio = tuple(ratio or (3.0 / 4.0, 4.0 / 3.0))  # default imagenet ratio range
    primary_tfl = [T.RandomResizedCrop(size, scale=scale, ratio=ratio, interpolation=interpolation)]
    if hflip > 0.0:
        primary_tfl += [T.RandomHorizontalFlip(p=hflip)]
    if vflip > 0.0:
        primary_tfl += [T.RandomVerticalFlip(p=vflip)]

    secondary_tfl = []
    disable_color_jitter = False
    if auto_augment:
        assert isinstance(auto_augment, str)
        # color jitter is typically disabled if AA/RA on,
        # this allows override without breaking old hparm cfgs
        disable_color_jitter = not force_color_jitter

        if auto_augment == "randaugment":
            if TORCHVISION_0_11:
                secondary_tfl += [T.RandAugment(interpolation=interpolation)]
            else:
                LOGGER.warning('"auto_augment=randaugment" requires torchvision >= 0.11.0. Disabling it.')

        elif auto_augment == "augmix":
            if TORCHVISION_0_13:
                secondary_tfl += [T.AugMix(interpolation=interpolation)]
            else:
                LOGGER.warning('"auto_augment=augmix" requires torchvision >= 0.13.0. Disabling it.')

        elif auto_augment == "autoaugment":
            if TORCHVISION_0_10:
                secondary_tfl += [T.AutoAugment(interpolation=interpolation)]
            else:
                LOGGER.warning('"auto_augment=autoaugment" requires torchvision >= 0.10.0. Disabling it.')

        else:
            raise ValueError(
                f'Invalid auto_augment policy: {auto_augment}. Should be one of "randaugment", '
                f'"augmix", "autoaugment" or None'
            )

    if not disable_color_jitter:
        secondary_tfl += [T.ColorJitter(brightness=hsv_v, contrast=hsv_v, saturation=hsv_s, hue=hsv_h)]

    final_tfl = [
        T.ToTensor(),
        T.Normalize(mean=torch.tensor(mean), std=torch.tensor(std)),
        T.RandomErasing(p=erasing, inplace=True),
    ]

    return T.Compose(primary_tfl + secondary_tfl + final_tfl)

class ClassifyLetterBox

# NOTE: keep this class for backward compatibility
class ClassifyLetterBox:
    """
    YOLOv8 LetterBox class for image preprocessing, designed to be part of a transformation pipeline, e.g.,
    T.Compose([LetterBox(size), ToTensor()]).

    Attributes:
        h (int): Target height of the image.
        w (int): Target width of the image.
        auto (bool): If True, automatically solves for short side using stride.
        stride (int): The stride value, used when 'auto' is True.
    """

    def __init__(self, size=(640, 640), auto=False, stride=32):
        """
        Initializes the ClassifyLetterBox class with a target size, auto-flag, and stride.

        Args:
            size (Union[int, Tuple[int, int]]): The target dimensions (height, width) for the letterbox.
            auto (bool): If True, automatically calculates the short side based on stride.
            stride (int): The stride value, used when 'auto' is True.
        """
        super().__init__()
        self.h, self.w = (size, size) if isinstance(size, int) else size
        self.auto = auto  # pass max size integer, automatically solve for short side using stride
        self.stride = stride  # used with auto

    def __call__(self, im):
        """
        Resizes the image and pads it with a letterbox method.

        Args:
            im (numpy.ndarray): The input image as a numpy array of shape HWC.

        Returns:
            (numpy.ndarray): The letterboxed and resized image as a numpy array.
        """
        imh, imw = im.shape[:2]
        r = min(self.h / imh, self.w / imw)  # ratio of new/old dimensions
        h, w = round(imh * r), round(imw * r)  # resized image dimensions

        # Calculate padding dimensions
        hs, ws = (math.ceil(x / self.stride) * self.stride for x in (h, w)) if self.auto else (self.h, self.w)
        top, left = round((hs - h) / 2 - 0.1), round((ws - w) / 2 - 0.1)

        # Create padded image
        im_out = np.full((hs, ws, 3), 114, dtype=im.dtype)
        im_out[top : top + h, left : left + w] = cv2.resize(im, (w, h), interpolation=cv2.INTER_LINEAR)
        return im_out

class CenterCrop

# NOTE: keep this class for backward compatibility
class CenterCrop:
    """YOLOv8 CenterCrop class for image preprocessing, designed to be part of a transformation pipeline, e.g.,
    T.Compose([CenterCrop(size), ToTensor()]).
    """

    def __init__(self, size=640):
        """Converts an image from numpy array to PyTorch tensor."""
        super().__init__()
        self.h, self.w = (size, size) if isinstance(size, int) else size

    def __call__(self, im):
        """
        Resizes and crops the center of the image using a letterbox method.

        Args:
            im (numpy.ndarray): The input image as a numpy array of shape HWC.

        Returns:
            (numpy.ndarray): The center-cropped and resized image as a numpy array.
        """
        imh, imw = im.shape[:2]
        m = min(imh, imw)  # min dimension
        top, left = (imh - m) // 2, (imw - m) // 2
        return cv2.resize(im[top : top + m, left : left + m], (self.w, self.h), interpolation=cv2.INTER_LINEAR)

class ToTensor

# NOTE: keep this class for backward compatibility
class ToTensor:
    """YOLOv8 ToTensor class for image preprocessing, i.e., T.Compose([LetterBox(size), ToTensor()])."""

    def __init__(self, half=False):
        """Initialize YOLOv8 ToTensor object with optional half-precision support."""
        super().__init__()
        self.half = half

    def __call__(self, im):
        """
        Transforms an image from a numpy array to a PyTorch tensor, applying optional half-precision and normalization.

        Args:
            im (numpy.ndarray): Input image as a numpy array with shape (H, W, C) in BGR order.

        Returns:
            (torch.Tensor): The transformed image as a PyTorch tensor in float32 or float16, normalized to [0, 1].
        """
        im = np.ascontiguousarray(im.transpose((2, 0, 1))[::-1])  # HWC to CHW -> BGR to RGB -> contiguous
        im = torch.from_numpy(im)  # to torch
        im = im.half() if self.half else im.float()  # uint8 to fp16/32
        im /= 255.0  # 0-255 to 0.0-1.0
        return im

base.py

class BaseDataset

class BaseDataset(Dataset):
    """
    Base dataset class for loading and processing image data.

    Args:
        img_path (str): Path to the folder containing images.
        imgsz (int, optional): Image size. Defaults to 640.
        cache (bool, optional): Cache images to RAM or disk during training. Defaults to False.
        augment (bool, optional): If True, data augmentation is applied. Defaults to True.
        hyp (dict, optional): Hyperparameters to apply data augmentation. Defaults to None.
        prefix (str, optional): Prefix to print in log messages. Defaults to ''.
        rect (bool, optional): If True, rectangular training is used. Defaults to False.
        batch_size (int, optional): Size of batches. Defaults to None.
        stride (int, optional): Stride. Defaults to 32.
        pad (float, optional): Padding. Defaults to 0.0.
        single_cls (bool, optional): If True, single class training is used. Defaults to False.
        classes (list): List of included classes. Default is None.
        fraction (float): Fraction of dataset to utilize. Default is 1.0 (use all data).

    Attributes:
        im_files (list): List of image file paths.
        labels (list): List of label data dictionaries.
        ni (int): Number of images in the dataset.
        ims (list): List of loaded images.
        npy_files (list): List of numpy file paths.
        transforms (callable): Image transformation function.
    """

    def __init__(
        self,
        img_path,
        imgsz=640,
        cache=False,
        augment=True,
        hyp=DEFAULT_CFG,
        prefix="",
        rect=False,
        batch_size=16,
        stride=32,
        pad=0.5,
        single_cls=False,
        classes=None,
        fraction=1.0,
    ):
        """Initialize BaseDataset with given configuration and options."""
        super().__init__()
        self.img_path = img_path
        self.imgsz = imgsz
        self.augment = augment
        self.single_cls = single_cls
        self.prefix = prefix
        self.fraction = fraction
        self.im_files = self.get_img_files(self.img_path)
        self.labels = self.get_labels()
        self.update_labels(include_class=classes)  # single_cls and include_class
        self.ni = len(self.labels)  # number of images
        self.rect = rect
        self.batch_size = batch_size
        self.stride = stride
        self.pad = pad
        if self.rect:
            assert self.batch_size is not None
            self.set_rectangle()

        # Buffer thread for mosaic images
        self.buffer = []  # buffer size = batch size
        self.max_buffer_length = min((self.ni, self.batch_size * 8, 1000)) if self.augment else 0

        # Cache images (options are cache = True, False, None, "ram", "disk")
        self.ims, self.im_hw0, self.im_hw = [None] * self.ni, [None] * self.ni, [None] * self.ni
        self.npy_files = [Path(f).with_suffix(".npy") for f in self.im_files]
        self.cache = cache.lower() if isinstance(cache, str) else "ram" if cache is True else None
        if (self.cache == "ram" and self.check_cache_ram()) or self.cache == "disk":
            self.cache_images()

        # Transforms
        self.transforms = self.build_transforms(hyp=hyp)

    def get_img_files(self, img_path):
        """Read image files."""
        try:
            f = []  # image files
            for p in img_path if isinstance(img_path, list) else [img_path]:
                p = Path(p)  # os-agnostic
                if p.is_dir():  # dir
                    f += glob.glob(str(p / "**" / "*.*"), recursive=True)
                    # F = list(p.rglob('*.*'))  # pathlib
                elif p.is_file():  # file
                    with open(p) as t:
                        t = t.read().strip().splitlines()
                        parent = str(p.parent) + os.sep
                        f += [x.replace("./", parent) if x.startswith("./") else x for x in t]  # local to global path
                        # F += [p.parent / x.lstrip(os.sep) for x in t]  # local to global path (pathlib)
                else:
                    raise FileNotFoundError(f"{self.prefix}{p} does not exist")
            im_files = sorted(x.replace("/", os.sep) for x in f if x.split(".")[-1].lower() in IMG_FORMATS)
            # self.img_files = sorted([x for x in f if x.suffix[1:].lower() in IMG_FORMATS])  # pathlib
            assert im_files, f"{self.prefix}No images found in {img_path}. {FORMATS_HELP_MSG}"
        except Exception as e:
            raise FileNotFoundError(f"{self.prefix}Error loading data from {img_path}\n{HELP_URL}") from e
        if self.fraction < 1:
            im_files = im_files[: round(len(im_files) * self.fraction)]  # retain a fraction of the dataset
        return im_files

    def update_labels(self, include_class: Optional[list]):
        """Update labels to include only these classes (optional)."""
        include_class_array = np.array(include_class).reshape(1, -1)
        for i in range(len(self.labels)):
            if include_class is not None:
                cls = self.labels[i]["cls"]
                bboxes = self.labels[i]["bboxes"]
                segments = self.labels[i]["segments"]
                keypoints = self.labels[i]["keypoints"]
                j = (cls == include_class_array).any(1)
                self.labels[i]["cls"] = cls[j]
                self.labels[i]["bboxes"] = bboxes[j]
                if segments:
                    self.labels[i]["segments"] = [segments[si] for si, idx in enumerate(j) if idx]
                if keypoints is not None:
                    self.labels[i]["keypoints"] = keypoints[j]
            if self.single_cls:
                self.labels[i]["cls"][:, 0] = 0

    def load_image(self, i, rect_mode=True):
        """Loads 1 image from dataset index 'i', returns (im, resized hw)."""
        im, f, fn = self.ims[i], self.im_files[i], self.npy_files[i]
        if im is None:  # not cached in RAM
            if fn.exists():  # load npy
                try:
                    im = np.load(fn)
                except Exception as e:
                    LOGGER.warning(f"{self.prefix}WARNING ⚠️ Removing corrupt *.npy image file {fn} due to: {e}")
                    Path(fn).unlink(missing_ok=True)
                    im = cv2.imread(f)  # BGR
            else:  # read image
                im = cv2.imread(f)  # BGR
            if im is None:
                raise FileNotFoundError(f"Image Not Found {f}")

            h0, w0 = im.shape[:2]  # orig hw
            if rect_mode:  # resize long side to imgsz while maintaining aspect ratio
                r = self.imgsz / max(h0, w0)  # ratio
                if r != 1:  # if sizes are not equal
                    w, h = (min(math.ceil(w0 * r), self.imgsz), min(math.ceil(h0 * r), self.imgsz))
                    im = cv2.resize(im, (w, h), interpolation=cv2.INTER_LINEAR)
            elif not (h0 == w0 == self.imgsz):  # resize by stretching image to square imgsz
                im = cv2.resize(im, (self.imgsz, self.imgsz), interpolation=cv2.INTER_LINEAR)

            # Add to buffer if training with augmentations
            if self.augment:
                self.ims[i], self.im_hw0[i], self.im_hw[i] = im, (h0, w0), im.shape[:2]  # im, hw_original, hw_resized
                self.buffer.append(i)
                if 1 < len(self.buffer) >= self.max_buffer_length:  # prevent empty buffer
                    j = self.buffer.pop(0)
                    if self.cache != "ram":
                        self.ims[j], self.im_hw0[j], self.im_hw[j] = None, None, None

            return im, (h0, w0), im.shape[:2]

        return self.ims[i], self.im_hw0[i], self.im_hw[i]

    def cache_images(self):
        """Cache images to memory or disk."""
        b, gb = 0, 1 << 30  # bytes of cached images, bytes per gigabytes
        fcn, storage = (self.cache_images_to_disk, "Disk") if self.cache == "disk" else (self.load_image, "RAM")
        with ThreadPool(NUM_THREADS) as pool:
            results = pool.imap(fcn, range(self.ni))
            pbar = TQDM(enumerate(results), total=self.ni, disable=LOCAL_RANK > 0)
            for i, x in pbar:
                if self.cache == "disk":
                    b += self.npy_files[i].stat().st_size
                else:  # 'ram'
                    self.ims[i], self.im_hw0[i], self.im_hw[i] = x  # im, hw_orig, hw_resized = load_image(self, i)
                    b += self.ims[i].nbytes
                pbar.desc = f"{self.prefix}Caching images ({b / gb:.1f}GB {storage})"
            pbar.close()

    def cache_images_to_disk(self, i):
        """Saves an image as an *.npy file for faster loading."""
        f = self.npy_files[i]
        if not f.exists():
            np.save(f.as_posix(), cv2.imread(self.im_files[i]), allow_pickle=False)

    def check_cache_ram(self, safety_margin=0.5):
        """Check image caching requirements vs available memory."""
        b, gb = 0, 1 << 30  # bytes of cached images, bytes per gigabytes
        n = min(self.ni, 30)  # extrapolate from 30 random images
        for _ in range(n):
            im = cv2.imread(random.choice(self.im_files))  # sample image
            ratio = self.imgsz / max(im.shape[0], im.shape[1])  # max(h, w)  # ratio
            b += im.nbytes * ratio**2
        mem_required = b * self.ni / n * (1 + safety_margin)  # GB required to cache dataset into RAM
        mem = psutil.virtual_memory()
        success = mem_required < mem.available  # to cache or not to cache, that is the question
        if not success:
            self.cache = None
            LOGGER.info(
                f"{self.prefix}{mem_required / gb:.1f}GB RAM required to cache images "
                f"with {int(safety_margin * 100)}% safety margin but only "
                f"{mem.available / gb:.1f}/{mem.total / gb:.1f}GB available, not caching images ⚠️"
            )
        return success

    def set_rectangle(self):
        """Sets the shape of bounding boxes for YOLO detections as rectangles."""
        bi = np.floor(np.arange(self.ni) / self.batch_size).astype(int)  # batch index
        nb = bi[-1] + 1  # number of batches

        s = np.array([x.pop("shape") for x in self.labels])  # hw
        ar = s[:, 0] / s[:, 1]  # aspect ratio
        irect = ar.argsort()
        self.im_files = [self.im_files[i] for i in irect]
        self.labels = [self.labels[i] for i in irect]
        ar = ar[irect]

        # Set training image shapes
        shapes = [[1, 1]] * nb
        for i in range(nb):
            ari = ar[bi == i]
            mini, maxi = ari.min(), ari.max()
            if maxi < 1:
                shapes[i] = [maxi, 1]
            elif mini > 1:
                shapes[i] = [1, 1 / mini]

        self.batch_shapes = np.ceil(np.array(shapes) * self.imgsz / self.stride + self.pad).astype(int) * self.stride
        self.batch = bi  # batch index of image

    def __getitem__(self, index):
        """Returns transformed label information for given index."""
        return self.transforms(self.get_image_and_label(index))

    def get_image_and_label(self, index):
        """Get and return label information from the dataset."""
        label = deepcopy(self.labels[index])  # requires deepcopy() https://github.com/ultralytics/ultralytics/pull/1948
        label.pop("shape", None)  # shape is for rect, remove it
        label["img"], label["ori_shape"], label["resized_shape"] = self.load_image(index)
        label["ratio_pad"] = (
            label["resized_shape"][0] / label["ori_shape"][0],
            label["resized_shape"][1] / label["ori_shape"][1],
        )  # for evaluation
        if self.rect:
            label["rect_shape"] = self.batch_shapes[self.batch[index]]
        return self.update_labels_info(label)

    def __len__(self):
        """Returns the length of the labels list for the dataset."""
        return len(self.labels)

    def update_labels_info(self, label):
        """Custom your label format here."""
        return label

    def build_transforms(self, hyp=None):
        """
        Users can customize augmentations here.

        Example:
            ```python
            if self.augment:
                # Training transforms
                return Compose([])
            else:
                # Val transforms
                return Compose([])
            ```
        """
        raise NotImplementedError

    def get_labels(self):
        """
        Users can customize their own format here.

        Note:
            Ensure output is a dictionary with the following keys:
            ```python
            dict(
                im_file=im_file,
                shape=shape,  # format: (height, width)
                cls=cls,
                bboxes=bboxes, # xywh
                segments=segments,  # xy
                keypoints=keypoints, # xy
                normalized=True, # or False
                bbox_format="xyxy",  # or xywh, ltwh
            )
            ```
        """
        raise NotImplementedError

bulid.py

class InfiniteDataLoader

class InfiniteDataLoader(dataloader.DataLoader):
    """
    Dataloader that reuses workers.

    Uses same syntax as vanilla DataLoader.
    """

    def __init__(self, *args, **kwargs):
        """Dataloader that infinitely recycles workers, inherits from DataLoader."""
        super().__init__(*args, **kwargs)
        object.__setattr__(self, "batch_sampler", _RepeatSampler(self.batch_sampler))
        self.iterator = super().__iter__()

    def __len__(self):
        """Returns the length of the batch sampler's sampler."""
        return len(self.batch_sampler.sampler)

    def __iter__(self):
        """Creates a sampler that repeats indefinitely."""
        for _ in range(len(self)):
            yield next(self.iterator)

    def reset(self):
        """
        Reset iterator.

        This is useful when we want to modify settings of dataset while training.
        """
        self.iterator = self._get_iterator()

class _RepeatSampler

class _RepeatSampler:
    """
    Sampler that repeats forever.

    Args:
        sampler (Dataset.sampler): The sampler to repeat.
    """

    def __init__(self, sampler):
        """Initializes an object that repeats a given sampler indefinitely."""
        self.sampler = sampler

    def __iter__(self):
        """Iterates over the 'sampler' and yields its contents."""
        while True:
            yield from iter(self.sampler)

def seed_worker(worker_id):  # noqa
    """Set dataloader worker seed https://pytorch.org/docs/stable/notes/randomness.html#dataloader."""
    worker_seed = torch.initial_seed() % 2**32
    np.random.seed(worker_seed)
    random.seed(worker_seed)


def build_yolo_dataset(cfg, img_path, batch, data, mode="train", rect=False, stride=32, multi_modal=False):
    """Build YOLO Dataset."""
    dataset = YOLOMultiModalDataset if multi_modal else YOLODataset
    return dataset(
        img_path=img_path,
        imgsz=cfg.imgsz,
        batch_size=batch,
        augment=mode == "train",  # augmentation
        hyp=cfg,  # TODO: probably add a get_hyps_from_cfg function
        rect=cfg.rect or rect,  # rectangular batches
        cache=cfg.cache or None,
        single_cls=cfg.single_cls or False,
        stride=int(stride),
        pad=0.0 if mode == "train" else 0.5,
        prefix=colorstr(f"{mode}: "),
        task=cfg.task,
        classes=cfg.classes,
        data=data,
        fraction=cfg.fraction if mode == "train" else 1.0,
    )


def build_grounding(cfg, img_path, json_file, batch, mode="train", rect=False, stride=32):
    """Build YOLO Dataset."""
    return GroundingDataset(
        img_path=img_path,
        json_file=json_file,
        imgsz=cfg.imgsz,
        batch_size=batch,
        augment=mode == "train",  # augmentation
        hyp=cfg,  # TODO: probably add a get_hyps_from_cfg function
        rect=cfg.rect or rect,  # rectangular batches
        cache=cfg.cache or None,
        single_cls=cfg.single_cls or False,
        stride=int(stride),
        pad=0.0 if mode == "train" else 0.5,
        prefix=colorstr(f"{mode}: "),
        task=cfg.task,
        classes=cfg.classes,
        fraction=cfg.fraction if mode == "train" else 1.0,
    )


def build_dataloader(dataset, batch, workers, shuffle=True, rank=-1):
    """Return an InfiniteDataLoader or DataLoader for training or validation set."""
    batch = min(batch, len(dataset))
    nd = torch.cuda.device_count()  # number of CUDA devices
    nw = min([os.cpu_count() // max(nd, 1), workers])  # number of workers
    sampler = None if rank == -1 else distributed.DistributedSampler(dataset, shuffle=shuffle)
    generator = torch.Generator()
    generator.manual_seed(6148914691236517205 + RANK)
    return InfiniteDataLoader(
        dataset=dataset,
        batch_size=batch,
        shuffle=shuffle and sampler is None,
        num_workers=nw,
        sampler=sampler,
        pin_memory=PIN_MEMORY,
        collate_fn=getattr(dataset, "collate_fn", None),
        worker_init_fn=seed_worker,
        generator=generator,
    )


def check_source(source):
    """Check source type and return corresponding flag values."""
    webcam, screenshot, from_img, in_memory, tensor = False, False, False, False, False
    if isinstance(source, (str, int, Path)):  # int for local usb camera
        source = str(source)
        is_file = Path(source).suffix[1:] in (IMG_FORMATS | VID_FORMATS)
        is_url = source.lower().startswith(("https://", "http://", "rtsp://", "rtmp://", "tcp://"))
        webcam = source.isnumeric() or source.endswith(".streams") or (is_url and not is_file)
        screenshot = source.lower() == "screen"
        if is_url and is_file:
            source = check_file(source)  # download
    elif isinstance(source, LOADERS):
        in_memory = True
    elif isinstance(source, (list, tuple)):
        source = autocast_list(source)  # convert all list elements to PIL or np arrays
        from_img = True
    elif isinstance(source, (Image.Image, np.ndarray)):
        from_img = True
    elif isinstance(source, torch.Tensor):
        tensor = True
    else:
        raise TypeError("Unsupported image type. For supported types see https://docs.ultralytics.com/modes/predict")

    return source, webcam, screenshot, from_img, in_memory, tensor


def load_inference_source(source=None, batch=1, vid_stride=1, buffer=False):
    """
    Loads an inference source for object detection and applies necessary transformations.

    Args:
        source (str, Path, Tensor, PIL.Image, np.ndarray): The input source for inference.
        batch (int, optional): Batch size for dataloaders. Default is 1.
        vid_stride (int, optional): The frame interval for video sources. Default is 1.
        buffer (bool, optional): Determined whether stream frames will be buffered. Default is False.

    Returns:
        dataset (Dataset): A dataset object for the specified input source.
    """
    source, stream, screenshot, from_img, in_memory, tensor = check_source(source)
    source_type = source.source_type if in_memory else SourceTypes(stream, screenshot, from_img, tensor)

    # Dataloader
    if tensor:
        dataset = LoadTensor(source)
    elif in_memory:
        dataset = source
    elif stream:
        dataset = LoadStreams(source, vid_stride=vid_stride, buffer=buffer)
    elif screenshot:
        dataset = LoadScreenshots(source)
    elif from_img:
        dataset = LoadPilAndNumpy(source)
    else:
        dataset = LoadImagesAndVideos(source, batch=batch, vid_stride=vid_stride)

    # Attach source types to the dataset
    setattr(dataset, "source_type", source_type)

    return dataset

dataset.py

class YOLODataset

class YOLODataset(BaseDataset):
    """
    Dataset class for loading object detection and/or segmentation labels in YOLO format.

    Args:
        data (dict, optional): A dataset YAML dictionary. Defaults to None.
        task (str): An explicit arg to point current task, Defaults to 'detect'.

    Returns:
        (torch.utils.data.Dataset): A PyTorch dataset object that can be used for training an object detection model.
    """

    def __init__(self, *args, data=None, task="detect", **kwargs):
        """Initializes the YOLODataset with optional configurations for segments and keypoints."""
        self.use_segments = task == "segment"
        self.use_keypoints = task == "pose"
        self.use_obb = task == "obb"
        self.data = data
        assert not (self.use_segments and self.use_keypoints), "Can not use both segments and keypoints."
        super().__init__(*args, **kwargs)

    def cache_labels(self, path=Path("./labels.cache")):
        """
        Cache dataset labels, check images and read shapes.

        Args:
            path (Path): Path where to save the cache file. Default is Path('./labels.cache').

        Returns:
            (dict): labels.
        """
        x = {"labels": []}
        nm, nf, ne, nc, msgs = 0, 0, 0, 0, []  # number missing, found, empty, corrupt, messages
        desc = f"{self.prefix}Scanning {path.parent / path.stem}..."
        total = len(self.im_files)
        nkpt, ndim = self.data.get("kpt_shape", (0, 0))
        if self.use_keypoints and (nkpt <= 0 or ndim not in {2, 3}):
            raise ValueError(
                "'kpt_shape' in data.yaml missing or incorrect. Should be a list with [number of "
                "keypoints, number of dims (2 for x,y or 3 for x,y,visible)], i.e. 'kpt_shape: [17, 3]'"
            )
        with ThreadPool(NUM_THREADS) as pool:
            results = pool.imap(
                func=verify_image_label,
                iterable=zip(
                    self.im_files,
                    self.label_files,
                    repeat(self.prefix),
                    repeat(self.use_keypoints),
                    repeat(len(self.data["names"])),
                    repeat(nkpt),
                    repeat(ndim),
                ),
            )
            pbar = TQDM(results, desc=desc, total=total)
            for im_file, lb, shape, segments, keypoint, nm_f, nf_f, ne_f, nc_f, msg in pbar:
                nm += nm_f
                nf += nf_f
                ne += ne_f
                nc += nc_f
                if im_file:
                    x["labels"].append(
                        {
                            "im_file": im_file,
                            "shape": shape,
                            "cls": lb[:, 0:1],  # n, 1
                            "bboxes": lb[:, 1:],  # n, 4
                            "segments": segments,
                            "keypoints": keypoint,
                            "normalized": True,
                            "bbox_format": "xywh",
                        }
                    )
                if msg:
                    msgs.append(msg)
                pbar.desc = f"{desc} {nf} images, {nm + ne} backgrounds, {nc} corrupt"
            pbar.close()

        if msgs:
            LOGGER.info("\n".join(msgs))
        if nf == 0:
            LOGGER.warning(f"{self.prefix}WARNING ⚠️ No labels found in {path}. {HELP_URL}")
        x["hash"] = get_hash(self.label_files + self.im_files)
        x["results"] = nf, nm, ne, nc, len(self.im_files)
        x["msgs"] = msgs  # warnings
        save_dataset_cache_file(self.prefix, path, x, DATASET_CACHE_VERSION)
        return x

    def get_labels(self):
        """Returns dictionary of labels for YOLO training."""
        self.label_files = img2label_paths(self.im_files)
        cache_path = Path(self.label_files[0]).parent.with_suffix(".cache")
        try:
            cache, exists = load_dataset_cache_file(cache_path), True  # attempt to load a *.cache file
            assert cache["version"] == DATASET_CACHE_VERSION  # matches current version
            assert cache["hash"] == get_hash(self.label_files + self.im_files)  # identical hash
        except (FileNotFoundError, AssertionError, AttributeError):
            cache, exists = self.cache_labels(cache_path), False  # run cache ops

        # Display cache
        nf, nm, ne, nc, n = cache.pop("results")  # found, missing, empty, corrupt, total
        if exists and LOCAL_RANK in {-1, 0}:
            d = f"Scanning {cache_path}... {nf} images, {nm + ne} backgrounds, {nc} corrupt"
            TQDM(None, desc=self.prefix + d, total=n, initial=n)  # display results
            if cache["msgs"]:
                LOGGER.info("\n".join(cache["msgs"]))  # display warnings

        # Read cache
        [cache.pop(k) for k in ("hash", "version", "msgs")]  # remove items
        labels = cache["labels"]
        if not labels:
            LOGGER.warning(f"WARNING ⚠️ No images found in {cache_path}, training may not work correctly. {HELP_URL}")
        self.im_files = [lb["im_file"] for lb in labels]  # update im_files

        # Check if the dataset is all boxes or all segments
        lengths = ((len(lb["cls"]), len(lb["bboxes"]), len(lb["segments"])) for lb in labels)
        len_cls, len_boxes, len_segments = (sum(x) for x in zip(*lengths))
        if len_segments and len_boxes != len_segments:
            LOGGER.warning(
                f"WARNING ⚠️ Box and segment counts should be equal, but got len(segments) = {len_segments}, "
                f"len(boxes) = {len_boxes}. To resolve this only boxes will be used and all segments will be removed. "
                "To avoid this please supply either a detect or segment dataset, not a detect-segment mixed dataset."
            )
            for lb in labels:
                lb["segments"] = []
        if len_cls == 0:
            LOGGER.warning(f"WARNING ⚠️ No labels found in {cache_path}, training may not work correctly. {HELP_URL}")
        return labels

    def build_transforms(self, hyp=None):
        """Builds and appends transforms to the list."""
        if self.augment:
            hyp.mosaic = hyp.mosaic if self.augment and not self.rect else 0.0
            hyp.mixup = hyp.mixup if self.augment and not self.rect else 0.0
            transforms = v8_transforms(self, self.imgsz, hyp)
        else:
            transforms = Compose([LetterBox(new_shape=(self.imgsz, self.imgsz), scaleup=False)])
        transforms.append(
            Format(
                bbox_format="xywh",
                normalize=True,
                return_mask=self.use_segments,
                return_keypoint=self.use_keypoints,
                return_obb=self.use_obb,
                batch_idx=True,
                mask_ratio=hyp.mask_ratio,
                mask_overlap=hyp.overlap_mask,
                bgr=hyp.bgr if self.augment else 0.0,  # only affect training.
            )
        )
        return transforms

    def close_mosaic(self, hyp):
        """Sets mosaic, copy_paste and mixup options to 0.0 and builds transformations."""
        hyp.mosaic = 0.0  # set mosaic ratio=0.0
        hyp.copy_paste = 0.0  # keep the same behavior as previous v8 close-mosaic
        hyp.mixup = 0.0  # keep the same behavior as previous v8 close-mosaic
        self.transforms = self.build_transforms(hyp)

    def update_labels_info(self, label):
        """
        Custom your label format here.

        Note:
            cls is not with bboxes now, classification and semantic segmentation need an independent cls label
            Can also support classification and semantic segmentation by adding or removing dict keys there.
        """
        bboxes = label.pop("bboxes")
        segments = label.pop("segments", [])
        keypoints = label.pop("keypoints", None)
        bbox_format = label.pop("bbox_format")
        normalized = label.pop("normalized")

        # NOTE: do NOT resample oriented boxes
        segment_resamples = 100 if self.use_obb else 1000
        if len(segments) > 0:
            # list[np.array(1000, 2)] * num_samples
            # (N, 1000, 2)
            segments = np.stack(resample_segments(segments, n=segment_resamples), axis=0)
        else:
            segments = np.zeros((0, segment_resamples, 2), dtype=np.float32)
        label["instances"] = Instances(bboxes, segments, keypoints, bbox_format=bbox_format, normalized=normalized)
        return label

    @staticmethod
    def collate_fn(batch):
        """Collates data samples into batches."""
        new_batch = {}
        keys = batch[0].keys()
        values = list(zip(*[list(b.values()) for b in batch]))
        for i, k in enumerate(keys):
            value = values[i]
            if k == "img":
                value = torch.stack(value, 0)
            if k in {"masks", "keypoints", "bboxes", "cls", "segments", "obb"}:
                value = torch.cat(value, 0)
            new_batch[k] = value
        new_batch["batch_idx"] = list(new_batch["batch_idx"])
        for i in range(len(new_batch["batch_idx"])):
            new_batch["batch_idx"][i] += i  # add target image index for build_targets()
        new_batch["batch_idx"] = torch.cat(new_batch["batch_idx"], 0)
        return new_batch


class YOLOMultiModalDataset(YOLODataset):
    """
    Dataset class for loading object detection and/or segmentation labels in YOLO format.

    Args:
        data (dict, optional): A dataset YAML dictionary. Defaults to None.
        task (str): An explicit arg to point current task, Defaults to 'detect'.

    Returns:
        (torch.utils.data.Dataset): A PyTorch dataset object that can be used for training an object detection model.
    """

    def __init__(self, *args, data=None, task="detect", **kwargs):
        """Initializes a dataset object for object detection tasks with optional specifications."""
        super().__init__(*args, data=data, task=task, **kwargs)

    def update_labels_info(self, label):
        """Add texts information for multi modal model training."""
        labels = super().update_labels_info(label)
        # NOTE: some categories are concatenated with its synonyms by `/`.
        labels["texts"] = [v.split("/") for _, v in self.data["names"].items()]
        return labels

    def build_transforms(self, hyp=None):
        """Enhances data transformations with optional text augmentation for multi-modal training."""
        transforms = super().build_transforms(hyp)
        if self.augment:
            # NOTE: hard-coded the args for now.
            transforms.insert(-1, RandomLoadText(max_samples=min(self.data["nc"], 80), padding=True))
        return transforms

tips:
pool.imap

未完待续