app.py

import json
import threading
from pathlib import Path

import gradio as gr
import torch
import torch.nn as nn
from PIL import Image
from safetensors.torch import load_file
from transformers import AutoImageProcessor, AutoModel
from huggingface_hub import snapshot_download

MODEL_REPO = "nzs234/siglip2-so400m-aesthetic-scorer-v1"
CACHE_DIR = Path("./model_cache")
_STATE_LOCK = threading.Lock()
_MODEL_READY = False
_MODEL_ERR = ""
processor = None
model = None
score_min = 1.0
score_max = 9.0


def infer_feature_dim(vision):
    cfg = getattr(vision, "config", None)
    for obj in [cfg, getattr(cfg, "vision_config", None) if cfg is not None else None]:
        if obj is None:
            continue
        for k in ("projection_dim", "hidden_size"):
            v = getattr(obj, k, None)
            if isinstance(v, int) and v > 0:
                return v
    proj = getattr(vision, "visual_projection", None)
    if isinstance(proj, nn.Linear):
        return int(proj.out_features)
    raise ValueError("cannot infer feature dim")


class Regressor(nn.Module):
    def __init__(self, backbone_dir: str, hidden_dim: int = 2048, dropout: float = 0.2):
        super().__init__()
        self.vision = AutoModel.from_pretrained(backbone_dir, local_files_only=True)
        feat_dim = infer_feature_dim(self.vision)
        h1 = int(hidden_dim)
        h2, h3, h4, h5 = 512, 256, 128, 32
        d1 = float(max(0.0, min(0.8, dropout if dropout > 0 else 0.3)))
        d2 = d1
        d3 = float(max(0.0, min(0.8, d1 * 0.67)))
        d4 = float(max(0.0, min(0.8, d1 * 0.33)))
        self.head = nn.Sequential(
            nn.LayerNorm(feat_dim),
            nn.Linear(feat_dim, h1),
            nn.ReLU(),
            nn.BatchNorm1d(h1),
            nn.Dropout(d1),
            nn.Linear(h1, h2),
            nn.ReLU(),
            nn.BatchNorm1d(h2),
            nn.Dropout(d2),
            nn.Linear(h2, h3),
            nn.ReLU(),
            nn.BatchNorm1d(h3),
            nn.Dropout(d3),
            nn.Linear(h3, h4),
            nn.ReLU(),
            nn.BatchNorm1d(h4),
            nn.Dropout(d4),
            nn.Linear(h4, h5),
            nn.ReLU(),
            nn.Linear(h5, 1),
        )

    def forward(self, pixel_values: torch.Tensor) -> torch.Tensor:
        if hasattr(self.vision, "get_image_features"):
            feats = self.vision.get_image_features(pixel_values=pixel_values)
            if not isinstance(feats, torch.Tensor):
                feats = feats.image_embeds if hasattr(feats, "image_embeds") else feats.pooler_output
        else:
            out = self.vision(pixel_values=pixel_values)
            feats = out.pooler_output if hasattr(out, "pooler_output") and out.pooler_output is not None else out.last_hidden_state[:, 0, :]
        feats = feats / (feats.norm(dim=1, keepdim=True) + 1e-8)
        x = self.head(feats).squeeze(-1)
        return torch.sigmoid(x)


def _ensure_loaded():
    global _MODEL_READY, _MODEL_ERR, processor, model, score_min, score_max
    if _MODEL_READY:
        return
    with _STATE_LOCK:
        if _MODEL_READY:
            return
        try:
            print("Downloading model repo snapshot...")
            local_repo = snapshot_download(repo_id=MODEL_REPO, repo_type="model", local_dir=str(CACHE_DIR))
            local_repo = Path(local_repo)
            meta = json.loads((local_repo / "metadata.json").read_text(encoding="utf-8"))
            model_cfg = meta.get("model", {})
            data_cfg = meta.get("data", {})

            processor = AutoImageProcessor.from_pretrained(str(local_repo / "backbone"), local_files_only=True, use_fast=False)
            model = Regressor(
                backbone_dir=str(local_repo / "backbone"),
                hidden_dim=int(model_cfg.get("hidden_dim", 2048)),
                dropout=float(model_cfg.get("dropout", 0.2)),
            )
            head_state = load_file(str(local_repo / "head.safetensors"), device="cpu")
            model.head.load_state_dict(head_state, strict=False)
            model.eval()

            score_min = float(data_cfg.get("score_min", 1.0))
            score_max = float(data_cfg.get("score_max", 9.0))
            _MODEL_READY = True
            _MODEL_ERR = ""
            print("Model loaded.")
        except Exception as e:
            _MODEL_ERR = str(e)
            raise


def predict(img):
    if img is None:
        return "error: no image"
    try:
        _ensure_loaded()
    except Exception:
        return f"error: model load failed: {_MODEL_ERR}"
    if img.mode != "RGB":
        img = img.convert("RGB")
    proc = processor(images=img, return_tensors="pt")
    with torch.inference_mode():
        pred_01 = model(proc["pixel_values"]).item()
    pred_01 = max(0.0, min(1.0, float(pred_01)))
    pred_score = pred_01 * (score_max - score_min) + score_min
    score_int = int(round(pred_score))
    score_int = max(int(score_min), min(int(score_max), score_int))
    return f"score_{score_int} (raw={pred_score:.4f})"


demo = gr.Interface(
    fn=predict,
    inputs=gr.Image(type="pil", label="Image"),
    outputs=gr.Textbox(label="Result"),
    title="SigLIP2 Aesthetic Scorer Demo",
    description="Upload image and get score_1..score_9",
    allow_flagging="never",
)

demo.launch(server_name="0.0.0.0", server_port=7860, show_api=False, ssr_mode=False, share=True)