I'm building a program which reads photos off an SD Card then resize the images and upload them to Flickr (note, it's a second SD Card reader, not the one on-board)

The photos are high-resolution JPG's. An example photo is a 8.1 MB JPG from a Canon Rebel T4i. They could possibly be of even higher resolution.

I want to upload a preview photo of eg ~100-150KB immediately after reading the photos in from the SD Card. The speed of the resize and upload is more important than high quality, though of course the the image should be recognizable.

For now, I've used imagemagick, and have tested numerous variables to increase the speed, including overclocking, using an additional USB-stick or storage, etc.

I'm currently getting down to ~6 seconds to resize the 8.1 MB to a ~150KB JPG. This is using the "sample" option, with a 10%/170KB resulting JPG. The output quality is high, in fact higher than it needs to be, but even when I reduce the quality the duration stays the time.

Any ideas for ... a) further improving the speed of the imagemagick convert (or maybe other imagemagick option) ? b) other tool/library? c) something entirely different?

I did a write up of my efforts so far here: http://blog.sunekaae.com/2013/04/imagemagick-resize-speed-on-raspberry-pi.html