Screenshots of Scrapy Splash?

I am trying to clean up the site by taking a screenshot of each page. So far, I've managed to put together the following code:

import json
import base64
import scrapy
from scrapy_splash import SplashRequest


class ExtractSpider(scrapy.Spider):
    name = 'extract'

    def start_requests(self):
        url = 'https://stackoverflow.com/'
        splash_args = {
            'html': 1,
            'png': 1
        }
        yield SplashRequest(url, self.parse_result, endpoint='render.json', args=splash_args)

    def parse_result(self, response):
        png_bytes = base64.b64decode(response.data['png'])

        imgdata = base64.b64decode(png_bytes)
        filename = 'some_image.png'
        with open(filename, 'wb') as f:
            f.write(imgdata)

      

        
        
        
      

    

It hits the site fine (like stackoverflow) and returns data for png_bytes, but when written to a file, it returns a broken image (not loading).

Is there a way to fix this, or alternatively find a better solution? I read that Splash Lua Scripts can do this, but couldn't find a way to implement it. Thank.