app.py

import gradio as gr
import numpy as np
from PIL import Image


def add_watermark(image):
    image = Image.fromarray(np.uint8(image))
    watermark = Image.open("watermark.png")

    image = image.convert("RGBA")
    watermark = watermark.convert("RGBA")
    
    width = image.width()
    height = image.height()

    image.paste(watermark, (width, height), watermark)
    return image

gr.Interface(fn=add_watermark,
             inputs="image",
             outputs="image",
             title="Add watermark" 
            ).launch();