app.py

import gradio as gr
import imageio
import numpy as np

def dummy(img, invert_mask):
  mask = img["mask"]
  if invert_mask and mask is not None:
    mask = 255 - np.array(mask)
  imageio.imwrite("output_image.png", mask)
  return img["image"], mask

with gr.Blocks() as demo:
  with gr.Row():
    img = gr.Image(tool="sketch", label="base image", show_label=True)
    img1 = gr.Image()
    img2 = gr.Image(label="mask image", show_label=True)
  invert = gr.Checkbox(label="Invert mask")
  btn = gr.Button()
  btn.click(dummy, [img, invert], [img1, img2])

demo.launch(debug=True)