A Django template tag for thumbnailing a block of HTML `img` tag using sorl-thumbnail and BeautifulSoup 4.

thumbnail_tags.py

from bs4 import BeautifulSoup

from django import template

from sorl.thumbnail.shortcuts import get_thumbnail
from sorl.thumbnail.conf import settings as sorl_settings

register = template.Library()

@register.filter(is_safe=True)
def html_thumbnails(value):
	soup = BeautifulSoup(value, "html.parser")
	
	for image in soup.find_all('img'):
		thumbnail = get_thumbnail(
			image.get('src'),
			image.get('geometry', sorl_settings.THUMBNAIL_FILTER_WIDTH),
			upscale=False
		)
		
		del image['geometry']
		
		image['src'] = thumbnail.url
		
	return str(soup)