403 Forbidden Response is seen for Images when using Dispatcher, a / is also appended to the end of the filename in the URL.
The extra slash is due to Apache's mod_dir module which appends / to a request URL that maps to a directory.
Set DirectorySlash directive to off in Apache's mod_dir module:
# enable dispatcher for ALL request if this is too restrictive,
# move it to another location
# RequestHeader add uid "admin"
DirectorySlash Directive http://httpd.apache.org/docs/current/mod/mod_dir.html#directoryslash Interference with Mod_Dir (Apache) https://docs.adobe.com/docs/en/dispatcher/disp-tshoot.html#Interference with mod_dir (Apache)