Redmine_thumbnails is a project mainly written in Ruby, it's free.
Redmine Thumbnails Plugin
= Redmine Thumbnails plugin
The Thumbnails plugin adds ability to insert attachment's thumbnails into issues, documents and wiki pages
== Features
== Getting the plugin
A copy of the plugin can be downloaded from {GitHub}[http://github.com/lest/redmine_thumbnails]
== Installation and Setup
== Example Usage
{{thumb(example.png)}}
{{thumb(example.png, issue=123)}}
{{thumb(example.png, width=300)}}
{{thumb(example.png, width=300, height=200)}}
== Project help
If you need help you can contact the maintainer at the Bug Tracker. The bug tracker is located at http://github.com/lest/redmine_thumbnails/issues