app.py

import gradio as gr
import base64
from io import BytesIO


def run(image):
    if image is None:
        raise gr.Error('No input image')

    buffer = BytesIO() 
    image.save(buffer, format='PNG')
    img_str = base64.b64encode(buffer.getvalue()).decode("utf-8")
    return img_str
    
with gr.Blocks() as demo:
    with gr.Row():
        with gr.Column():
            image = gr.Image(type='pil', interactive=True)
            submit = gr.Button()
        output_text = gr.Textbox(interactive=False)

    submit.click(
        fn=run,
        inputs=[image],
        outputs=[output_text],
    )

demo.launch(show_error=True)