app.py

from fastapi import FastAPI, Response, Depends
from fastapi.middleware.cors import CORSMiddleware
import torch
from torch.cuda.amp import autocast
from diffusers import DiffusionPipeline
from io import BytesIO
import os

app = FastAPI()

app.add_middleware(
    CORSMiddleware,
    allow_credentials=True,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"]
)

model_id = "stabilityai/stable-diffusion-xl-base-1.0"
device = "cuda" if torch.cuda.is_available() else "cpu"

pipe = DiffusionPipeline.from_pretrained(model_id, torch_dtype=torch.float32, use_safetensors=True, variant="fp16")

pipe = pipe.to(device)

def get_secret(secret_key: str = Depends(lambda x: x.headers.get("secret-key"))):
    return secret_key

@app.post("/")
def generate(prompt: str, secret: str = Depends(get_secret)):
    if secret != os.getenv("SECRET_KEY"):
        return Response(content="Unauthorized", status_code=401)

    with autocast(device):
        image = pipe(prompt, guidance_scale=8.5).images[0]

    buffer = BytesIO()
    image.save(buffer, format="PNG") 
    buffer.seek(0)

    return Response(content=buffer.getvalue(), media_type="image/png")