[Doitsu]

@nirosan

Copy a .png file to your plugin folder, rename it to cover.png and test the following code:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sys, os, string, random

def run(bk):
    image_name = 'cover.png'
    mime_type = 'image/png'
    image_path = os.path.join(bk._w.plugin_dir, bk._w.plugin_name, image_name)
    
    if os.path.isfile(image_path):
        with open(image_path, 'rb') as f:
            image_data = f.read()
    
        try:
            bk.addfile(image_name, image_name, image_data, mime_type)
        except:
            random_prefix = ''.join(random.choices(string.ascii_uppercase + string.digits, k=6))
            image_name = random_prefix + image_name
            bk.addfile(image_name, image_name, image_data, mime_type)
            
    return 0

It should add a cover.png file to your epub.