INFERENCE.py

"""PixelModel v3 inference from model.safetensors (standalone).

Needs only: model.safetensors, model.py, vocab.json, torch. No model.png,
no config.json - the architecture config is read from the safetensors header.
Produces output identical to main.py for the same prompt and resolution.

    python convert_to_safetensors.py
    python INFERENCE.py "a red double decker bus" --out bus.png
"""

from __future__ import annotations

import argparse
import json

import numpy as np
import torch
from PIL import Image
from safetensors import safe_open

from model import (
    ModelConfig, PixelModelV3, load_vocab, encode_caption, make_coord_grid,
)


def load_from_safetensors(path, device):
    with safe_open(path, framework="pt", device="cpu") as f:
        meta = f.metadata() or {}
        cfg = ModelConfig.from_json(json.loads(meta["config"]))
        model = PixelModelV3(cfg)
        state = {k: f.get_tensor(k) for k in f.keys()}
    model.load_state_dict(state)
    model.to(device).eval()
    return model, cfg


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("prompt")
    ap.add_argument("--out", default="out.png")
    ap.add_argument("--res", type=int, default=128)
    ap.add_argument("--safetensors", default="model.safetensors")
    ap.add_argument("--vocab", default="vocab.json")
    ap.add_argument("--device", default="cpu")
    args = ap.parse_args()

    model, cfg = load_from_safetensors(args.safetensors, args.device)
    vocab = load_vocab(args.vocab)

    tokens = encode_caption(args.prompt, vocab, cfg.max_tokens)
    tokens = torch.from_numpy(tokens).long().unsqueeze(0).to(args.device)
    coords = make_coord_grid(args.res, args.res, device=args.device,
                             dtype=torch.float32).unsqueeze(0)
    with torch.no_grad():
        rgb = model(tokens, coords)
    img = (rgb.clamp(0, 1).reshape(args.res, args.res, 3).cpu().numpy() * 255.0
           ).round().astype(np.uint8)
    Image.fromarray(img, "RGB").save(args.out)
    print(f'[inference] "{args.prompt}" @ {args.res}x{args.res} -> {args.out}')


if __name__ == "__main__":
    main()