Im developing web-application with Merb and im looking for some safe and stable image processing library. I used to work with Imagick in php, then moved to ruby and start us
I too have encountered this issue - the solution is to force garbage collection.
When you have reassigned the image variable to a new image simply use GC.start to ensure the old reference is released from memory.
On later versions of RMagick, I also believe you can also call destroy! on the image when you have finished processing it.
A combination of the two would probably ensure you are covered, but im not sure of the real life impact on performance (I would assume it is negligible i most cases).
Alternatively, you could use mini-magick which is a wrapper for the ImageMagick commandline client.