Image resizing with pThumb
The option &pOtions passes options to the pThumb snippet.
In this example the highest RS image resolution is targeted (option rssize is not specified) for 550 pixels width resizing at quality 90: w=550&q=90
If pOptions option is not specified, URL target the original image file.
[[xrs? &action=`single` &rsid=`181` &tpl=`itpl.rssingle.img` &extend=`1` &pOptions=`w=550&q=90` ]]
pThumb is A fork of phpThumbOf 1.4.0. pThumb is a lightweight, efficient, and actively maintained replacement for phpThumbOf. It offers most of the functionality of its predecessor while adding new features, and offering some potentially dramatic speed improvements on sites... It allows you to use the graphics libraries on an Apache server to make modifications to images on-the-fly and cache the resized files.
pThumb website: https://github.com/modxcms/pThumb
All pThumb options: http://phpthumb.sourceforge.net/demo/docs/phpthumb.readme.txt
pThumb extra page on MODX website: https://modx.com/extras/package/pthumb