nginx.conf

proxy_cache_path /var/cache/cf-images levels=1:2 keys_zone=CF_IMAGES:10m inactive=7d max_size=10MB;

server {
	# ... here goes the rest of your config.

	# Proxy example.com/cfimg/original/path/image.jpg?cf=width=100,quality=80
	# to example.com/cdn-cgi/image/width=100,quality=80/original/path/image.jpg
	location ~* ^/cfimg/(.*)$ {
		resolver 1.1.1.1;
	
		proxy_pass https://your-cloudflare-domain.com/cdn-cgi/image/$arg_cf/$1;

		add_header X-CF-Cache $upstream_cache_status;

		proxy_cache CF_IMAGES;
		proxy_cache_key "$host$request_uri$http_accept";
		proxy_cache_valid 200 30d;
		proxy_cache_use_stale error timeout invalid_header updating http_500 http_502 http_503 http_504;
	}
}