app.py

import os
import random
import time
from typing import Optional

import gradio as gr
import torch
from diffusers import StableDiffusionPipeline, EulerAncestralDiscreteScheduler

# -----------------------------
# Device & Precision
# -----------------------------
USE_CUDA = torch.cuda.is_available()
DTYPE = torch.float16 if USE_CUDA else torch.float32
DEVICE = "cuda" if USE_CUDA else "cpu"

MODEL_ID = os.environ.get("MODEL_ID", "runwayml/stable-diffusion-v1-5")

pipe: Optional[StableDiffusionPipeline] = None


def load_pipeline():
    """Load and configure the Stable Diffusion pipeline once at startup."""
    global pipe
    t0 = time.time()
    pipe = StableDiffusionPipeline.from_pretrained(
        MODEL_ID,
        torch_dtype=DTYPE,
        safety_checker=None,  # Keep None for faster demos
    )

    # Use a fast, good-quality scheduler
    pipe.scheduler = EulerAncestralDiscreteScheduler.from_config(pipe.scheduler.config)

    pipe = pipe.to(DEVICE)

    # Optional memory optimization on GPU
    if USE_CUDA:
        try:
            pipe.enable_attention_slicing()
            pipe.enable_xformers_memory_efficient_attention()
        except Exception:
            pass

    t1 = time.time()
    print(f"Pipeline loaded in {t1 - t0:.2f}s on {DEVICE} (dtype={DTYPE}).")


# Load on import (Space boot)
load_pipeline()


def generate_image(
    prompt: str,
    negative_prompt: str,
    steps: int,
    guidance: float,
    width: int,
    height: int,
    seed: int,
):
    if not prompt or len(prompt.strip()) == 0:
        raise gr.Error("Please enter a prompt.")

    width = max(256, min(1024, width))
    height = max(256, min(1024, height))

    if seed == -1:
        seed = random.randint(0, 2**31 - 1)
    generator = torch.Generator(device=DEVICE).manual_seed(seed)

    with torch.autocast(DEVICE, enabled=USE_CUDA):
        image = pipe(
            prompt=prompt,
            negative_prompt=negative_prompt or None,
            num_inference_steps=int(steps),
            guidance_scale=float(guidance),
            width=int(width),
            height=int(height),
            generator=generator,
        ).images[0]

    return image, seed


# -----------------------------
# Gradio UI
# -----------------------------
with gr.Blocks(title="Stable Diffusion Image Generator", css="footer {visibility: hidden}") as demo:
    gr.Markdown(
        """
        # 🧠 Stable Diffusion Image Generator
        Type a prompt and generate an image using **Stable Diffusion v1.5**.
        
        **Tip:** For consistent results, set a fixed seed. Use `-1` for random seed.
        """
    )

    with gr.Row():
        with gr.Column(scale=3):
            prompt = gr.Textbox(
                label="Prompt",
                placeholder="a cinematic portrait of an astronaut relaxing in a tropical cafe, 35mm photo, bokeh, soft light",
                lines=3,
            )
            negative_prompt = gr.Textbox(
                label="Negative Prompt (optional)",
                placeholder="blurry, low quality, extra fingers, text, watermark",
                lines=2,
            )
            with gr.Row():
                steps = gr.Slider(5, 50, value=25, step=1, label="Steps")
                guidance = gr.Slider(0.0, 15.0, value=7.5, step=0.5, label="Guidance Scale")
            with gr.Row():
                width = gr.Slider(256, 1024, value=512, step=64, label="Width")
                height = gr.Slider(256, 1024, value=512, step=64, label="Height")
            seed = gr.Number(value=-1, precision=0, label="Seed (-1 for random)")
            generate_btn = gr.Button("Generate", variant="primary")
        with gr.Column(scale=4):
            out_image = gr.Image(label="Result", type="pil")
            out_seed = gr.Number(label="Used Seed", interactive=False)

    examples = gr.Examples(
        examples=[
            [
                "ultra-detailed watercolor of a koi fish swirling through clouds, ethereal, pastel palette",
                "lowres, noisy, text",
                28,
                7.5,
                512,
                512,
                1234,
            ],
            [
                "cozy cyberpunk alley coffee shop at dusk, volumetric lighting, rain reflections, 4k",
                "low quality, oversaturated",
                25,
                6.5,
                640,
                384,
                -1,
            ],
            [
                "studio photo of a cute corgi wearing sunglasses, soft light, shallow depth of field",
                "text, watermark, blurry",
                22,
                7.0,
                512,
                512,
                2024,
            ],
        ],
        inputs=[prompt, negative_prompt, steps, guidance, width, height, seed],
    )

    generate_btn.click(
        fn=generate_image,
        inputs=[prompt, negative_prompt, steps, guidance, width, height, seed],
        outputs=[out_image, out_seed],
        api_name="generate",
    )

if __name__ == "__main__":
    demo.launch()