venv/lib/python3.11/site-packages/trl/models/auxiliary_modules.py

# Copyright 2020-2025 The HuggingFace Team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import os

import torch
import torch.nn as nn
import torchvision
from huggingface_hub import hf_hub_download
from huggingface_hub.utils import EntryNotFoundError
from transformers import CLIPModel, is_torch_npu_available, is_torch_xpu_available


class MLP(nn.Module):
    def __init__(self):
        super().__init__()
        self.layers = nn.Sequential(
            nn.Linear(768, 1024),
            nn.Dropout(0.2),
            nn.Linear(1024, 128),
            nn.Dropout(0.2),
            nn.Linear(128, 64),
            nn.Dropout(0.1),
            nn.Linear(64, 16),
            nn.Linear(16, 1),
        )

    def forward(self, embed):
        return self.layers(embed)


class AestheticScorer(torch.nn.Module):
    """
    This model attempts to predict the aesthetic score of an image. The aesthetic score
    is a numerical approximation of how much a specific image is liked by humans on average.
    This is from https://github.com/christophschuhmann/improved-aesthetic-predictor
    """

    def __init__(self, *, dtype, model_id, model_filename):
        super().__init__()
        self.clip = CLIPModel.from_pretrained("openai/clip-vit-large-patch14")
        self.normalize = torchvision.transforms.Normalize(
            mean=[0.48145466, 0.4578275, 0.40821073], std=[0.26862954, 0.26130258, 0.27577711]
        )
        self.target_size = 224
        self.mlp = MLP()
        try:
            cached_path = hf_hub_download(model_id, model_filename)
        except EntryNotFoundError:
            cached_path = os.path.join(model_id, model_filename)
        state_dict = torch.load(cached_path, map_location=torch.device("cpu"), weights_only=True)
        self.mlp.load_state_dict(state_dict)
        self.dtype = dtype
        self.eval()

    def __call__(self, images):
        device = next(self.parameters()).device
        images = torchvision.transforms.Resize(self.target_size)(images)
        images = self.normalize(images).to(self.dtype).to(device)
        embed = self.clip.get_image_features(pixel_values=images)
        # normalize embedding
        embed = embed / torch.linalg.vector_norm(embed, dim=-1, keepdim=True)
        reward = self.mlp(embed).squeeze(1)
        return reward


def aesthetic_scorer(hub_model_id, model_filename):
    scorer = AestheticScorer(
        model_id=hub_model_id,
        model_filename=model_filename,
        dtype=torch.float32,
    )
    if is_torch_npu_available():
        scorer = scorer.npu()
    elif is_torch_xpu_available():
        scorer = scorer.xpu()
    else:
        scorer = scorer.cuda()

    def _fn(images, prompts, metadata):
        images = (images).clamp(0, 1)
        scores = scorer(images)
        return scores, {}

    return _fn