Better JPEG Lossless Resave plug-in for Adobe Photoshop is a tool designed to avoid recompression loss when editing and resaving JPEG images in Photoshop. The plug-in takes advantage of the fact that JPEG images consist of a number of small independent blocks and does not recompress blocks that don't have to be changed.
The plug-in consists of two parts: Better JPEG Lossless Import and Better JPEG Lossless Export.
Free download