DroidAssets allows you to generate all the assets you need for your Android application in record time. Drag-and-drop an asset from the res/drawable-{density} folder, and this asset will be generated for all the other densities you need. This works not only for simple PNG's, but also 9-patches.
Resize PNG assets
Regenerate 9-patches for reduced images
Place the generated images in the right drawable folder
What’s new in version 1.1.0
Updated on Aug 15 2013
Version 1.1.0:
Fix 9-patch for images 1px wide that could be cut in some cases
Fix vertical 9-patch that was reversed
Fix 9-patch that could extend in the corners sometimes