I second this, for a recent e-commerce project we started using nginx's image_filter but the quality of the resized images was unacceptable. We ended up using

I second this, for a recent e-commerce project we started using nginx's image_filter but the quality of the resized images was unacceptable. We ended up using Thumbor, which was able to give us much better looking images (but at the cost of being extremely difficult to deploy on the CentOS 6.x servers we had at that time).