I know the problem Anahata's talking about. The problem is that JPEG is a lossy compression format, and like all lossy compression formats it introduces compression artifacts. The result of this is the blurring of any sharp transition between colours. On photos this is fine - photographic film and CCDs are inherently noisy, so what looks a consistent grey, for example, will actually be dotty darker and brighter pixels as you get closer in. So this blurring is fine for photos.

Trouble is that it's hopeless for text or line-drawing stuff. For these, any blurring due to compression is instantly visible, because the picture starts looking like it's slightly out of focus. Obviously the less compression you use, the better it'll look, so you may get away with some compression and still have a useable picture. It's not ideal though. I've never used the PNP format, but checking on the web I see that it's also a lossy compression format, so I wouldn't recommend using that either.

If you want line-drawings that come out correctly (ie. unblurred), then you want a non-lossy compression format. The two main candidates here are GIF and PNG - PNG isn't as widely-known yet, but it tends to perform better than GIF. All modern graphics packages should support both, although some very old packages may only do GIF. Either way, these compress the data using similar techniques to Winzip, so that the picture you get out is the same as the picture you put in.

Although the image quality will be better, GIF and PNG files will usually be larger than JPEG files. Even large images will usually compress very well though, and in today's era of high bandwidth and near-infinite disk space, no-one will much care about the difference in size between a 10K file and a 20K file.

Graham.