Let's take screenshots of a bunch of games.

mgba-index-screenshots.py

import mgba.core
import mgba.image
import mgba.log

import os, os.path
import sys

from concurrent.futures import ThreadPoolExecutor

logger = mgba.log.NullLogger()
mgba.log.installDefault(logger)

def runSingle(root, name, out="."):
        core = mgba.core.loadPath(os.path.join(root, name))
        if not core:
                return
        screen = mgba.image.Image(*core.desiredVideoDimensions())
        core.setVideoBuffer(screen)
        core.reset()
        print('Starting %s' % name)

        for frame in [30, 60, 300, 900, 1800, 3600]:
                while core.frameCounter() < frame:
                        core.runFrame()

                with open(os.path.join(out, '%s-%d.png' % (name, frame)), 'wb') as f:
                        screen.savePNG(f)
        print('Finished %s' % name)

if __name__ == '__main__':
        with ThreadPoolExecutor(max_workers=4) as e:
                for dirname, _, files in os.walk(sys.argv[1]):
                        for f in files:
                                e.submit(runSingle, dirname, f, sys.argv[2])