gradio/demo/demo1.py

import gradio as gr
import cv2

def to_black(image):
    output = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    return output

# GUI      http://127.0.0.1:7860/
interface = gr.Interface(fn=to_black, inputs="image", outputs="image",  examples=[["test.png"]])
interface.launch()