Redirect to minified version images

.htaccess

<IfModule mod_rewrite.c>

  RewriteEngine On
  RewriteBase /

  # %{ENV:BASE} is current url path
  # See http://stackoverflow.com/questions/21062290/set-rewritebase-to-the-current-folder-path-dynamically
  RewriteCond %{REQUEST_URI}::$1 ^(.*?/)(.*)::\2$
  RewriteRule ^(.*)$ - [E=BASE:%1]

  # foo/xxx.png => foo/min/xxx-min.png if exists
  RewriteCond %{DOCUMENT_ROOT}%{ENV:BASE}$1min/$2-min.$3 -f
  RewriteRule ^(.*\/)(.*)\.(png|jpg)$ %{ENV:BASE}$1min/$2-min.$3

  # foo/xxx.png => foo/xxx-min.png if exists
  # RewriteCond %{DOCUMENT_ROOT}%{ENV:BASE}$1$2-min.$3 -f
  # RewriteRule ^(.*\/)(.*)\.(png|jpg)$ %{ENV:BASE}$1$2-min.$3

</IfModule>