rembg/sessions/base.py

import os
from typing import Dict, List, Tuple

import numpy as np
import onnxruntime as ort
from PIL import Image
from PIL.Image import Image as PILImage


class BaseSession:
    """This is a base class for managing a session with a machine learning model."""

    def __init__(
        self,
        model_name: str,
        sess_opts: ort.SessionOptions,
        providers=None,
        *args,
        **kwargs
    ):
        """Initialize an instance of the BaseSession class."""
        self.model_name = model_name

        self.providers = []

        _providers = ort.get_available_providers()
        if providers:
            for provider in providers:
                if provider in _providers:
                    self.providers.append(provider)
        else:
            self.providers.extend(_providers)

        self.inner_session = ort.InferenceSession(
            str(self.__class__.download_models(*args, **kwargs)),
            providers=self.providers,
            sess_options=sess_opts,
        )

    def normalize(
        self,
        img: PILImage,
        mean: Tuple[float, float, float],
        std: Tuple[float, float, float],
        size: Tuple[int, int],
        *args,
        **kwargs
    ) -> Dict[str, np.ndarray]:
        im = img.convert("RGB").resize(size, Image.Resampling.LANCZOS)

        im_ary = np.array(im)
        im_ary = im_ary / np.max(im_ary)

        tmpImg = np.zeros((im_ary.shape[0], im_ary.shape[1], 3))
        tmpImg[:, :, 0] = (im_ary[:, :, 0] - mean[0]) / std[0]
        tmpImg[:, :, 1] = (im_ary[:, :, 1] - mean[1]) / std[1]
        tmpImg[:, :, 2] = (im_ary[:, :, 2] - mean[2]) / std[2]

        tmpImg = tmpImg.transpose((2, 0, 1))

        return {
            self.inner_session.get_inputs()[0]
            .name: np.expand_dims(tmpImg, 0)
            .astype(np.float32)
        }

    def predict(self, img: PILImage, *args, **kwargs) -> List[PILImage]:
        raise NotImplementedError

    @classmethod
    def checksum_disabled(cls, *args, **kwargs):
        return os.getenv("MODEL_CHECKSUM_DISABLED", None) is not None

    @classmethod
    def u2net_home(cls, *args, **kwargs):
        return os.path.expanduser(
            os.getenv(
                "U2NET_HOME", os.path.join(os.getenv("XDG_DATA_HOME", "~"), ".u2net")
            )
        )

    @classmethod
    def download_models(cls, *args, **kwargs):
        raise NotImplementedError

    @classmethod
    def name(cls, *args, **kwargs):
        raise NotImplementedError