ImageIO does this reasonably efficiently. After you load the image, ask for the Raster from the resulting BufferedImage and get the DataBuffer from it.
I'm familiar with this technique- using it atm- but my game may involve loading a lot of images in a short timeframe, so I'd like to cut down on overhead as much as possible. Plus, I'm feeding the image data as textures directly to JOGL, so Image objects themselves are redundant.
I'd seen the list before, but on second inspection the FM Software GifDecoder seems promising... sadly, the JPEG baseline decoder and encoder isn't accessible atm. I may be able to adapt the DevIL source to my requirements in any case. Thanks again.