MODX Cloud Nginx "Web Rule" for Adaptive Images script https://github.com/MattWilcox/Adaptive-Images

nginx.conf

# Adaptive-Images rewrite
# this example bypasses requests for any images in the root assets and ai-cache folders 
rewrite ^/(?!assets|ai-cache).*\.(jpe?g|gif|png)$ /adaptive-images.php last;

location / {
    try_files $uri $uri/ @modx-rewrite;
}