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")

    watermark = watermark.resize((image.width, image.height))
    image.paste(watermark,(0,0),watermark)

    return image

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