Raster image editing can do wonders for photos that have been scarred by the effects of repeated saving or overdoing it with the JPEG compression. You can use all sorts of editing tools to tame distracting noise, smooth out rough patches and selectively sharpen the important stuff. as Visuals Clipping points out. you can't always get back the information that's been lost from the compression - so be careful with how you adjust things because over-processing can end up making the blocky edges and unwanted textures all the more noticeable.