ImageMagick comes with an utility called convert. One use I frequently have for it is to run my digital photos thru it, like so: convert image.jpg conv/image.jpg. So what I do is simply to uncompress and recompress it. This is of course a lossy process, but in practice I can’t tell any difference from original and recompressed even when I zoom quite far in. And the disk space saving can be quite significant, up to 50%.
