import gradio as gr
import imageio

def dummy(img):
    imageio.imwrite("output_image.png", img["mask"])
    return img["image"], img["mask"]

with gr.Blocks() as demo:
    with gr.Row():
        img = gr.Image(tool="sketch", label="base image", show_label=True, source="upload", type="pil")
        img2 = gr.Image(label="mask image", show_label=True, type="pil")
    btn = gr.Button()
    btn.click(dummy, inputs=img, outputs=[img, img2])

demo.launch(debug=True)