for use with PySimpleGUI

image_helper.py

import PIL.Image
import io


def image_as_png_bytes(file_path, resize=None):
    """
    Open an image file and convert it into PNG formated bytes, resize optional.
    Return tuple (bytes, <dict from PIL.Image.info>)
    """
    img = PIL.Image.open(file_path)
    cur_width, cur_height = img.size
    if resize:
        new_width, new_height = resize
        scale = min(new_height / cur_height, new_width / cur_width)
        img = img.resize(
            (int(cur_width * scale), int(cur_height * scale)),
            PIL.Image.Resampling.LANCZOS,
        )
    with io.BytesIO() as bio:
        img.save(bio, format='PNG')
        return bio.getvalue(), img.info