core/image_generator.py

# core/image_generator.py
import os
import torch
from diffusers import StableDiffusionXLPipeline
from huggingface_hub import hf_hub_download
from pathlib import Path
from typing import List

# ---------------- MODEL CONFIG ----------------
MODEL_REPO = "SG161222/RealVisXL_V4.0"
MODEL_FILENAME = "realvisxlV40_v40LightningBakedvae.safetensors"
MODEL_DIR = Path("/tmp/models/realvisxl_v4")
os.makedirs(MODEL_DIR, exist_ok=True)

# ---------------- MODEL DOWNLOAD ----------------
def download_model() -> Path:
    """
    Downloads RealVisXL V4.0 model if not present.
    Returns the local model path.
    """
    model_path = MODEL_DIR / MODEL_FILENAME
    if not model_path.exists():
        print("[ImageGen] Downloading RealVisXL V4.0 model...")
        model_path = hf_hub_download(
            repo_id=MODEL_REPO,
            filename=MODEL_FILENAME,
            local_dir=str(MODEL_DIR),
            force_download=False,
        )
        print(f"[ImageGen] Model downloaded to: {model_path}")
    else:
        print("[ImageGen] Model already exists. Skipping download.")
    return model_path

# ---------------- PIPELINE LOAD ----------------
def load_pipeline() -> StableDiffusionXLPipeline:
    """
    Loads the RealVisXL V4.0 model for image generation.
    """
    model_path = download_model()
    print("[ImageGen] Loading model into pipeline...")
    pipe = StableDiffusionXLPipeline.from_single_file(
        str(model_path),
        torch_dtype=torch.float16 if torch.cuda.is_available() else torch.float32,
    )
    if torch.cuda.is_available():
        pipe.to("cuda")
    print("[ImageGen] Model ready.")
    return pipe

# ---------------- GLOBAL PIPELINE CACHE ----------------
pipe: StableDiffusionXLPipeline | None = None

# ---------------- IMAGE GENERATION ----------------
def generate_images(prompt: str, seed: int = None, num_images: int = 3) -> List:
    """
    Generates high-quality images using RealVisXL V4.0.
    Supports deterministic generation using a seed.
    
    Args:
        prompt (str): Text prompt for image generation.
        seed (int, optional): Seed for deterministic generation.
        num_images (int): Number of images to generate.
        
    Returns:
        List: Generated PIL images.
    """
    global pipe
    if pipe is None:
        pipe = load_pipeline()

    print(f"[ImageGen] Generating {num_images} image(s) for prompt: '{prompt}' with seed={seed}")
    images = []

    for i in range(num_images):
        generator = None
        if seed is not None:
            device = "cuda" if torch.cuda.is_available() else "cpu"
            generator = torch.Generator(device).manual_seed(seed + i)  # slightly vary keyframes

        result = pipe(prompt, num_inference_steps=30, generator=generator).images[0]
        images.append(result)

    print(f"[ImageGen] Generated {len(images)} images successfully.")
    return images