Converting a standard JPEG into a progressive one?

April 22, 2005 6:23 PM

Is it possible to convert a standard JPEG into a progressive one without losing quality? If so, what can I use to do it?
posted by Nikolai to Computers & Internet (7 answers total)

Yes, it is technically possible. I'm afraid I don't know any software that does it though…
posted by fvw at 6:40 PM on April 22, 2005

Try resaving in photoshop, with the highest image quality.
posted by slipperywhenwet at 6:43 PM on April 22, 2005

Doing it in Photoshop won't work.

Using the jpegtran app provided as part of the Independent JPEG Group's reference JPEG impementation is, as far as I know, the only way to do this. It's a command-line utility that you can compile on pretty much any Unix machine, and there are Windows binaries available as well. There also appear to be a slew of apps built on the IJG/jpegtran codebase, although I have no idea about any of these.
posted by delfuego at 8:32 PM on April 22, 2005

BTW, in general recompressing a JPEG doesn't really hurt quality very much. I'm not positive there's not something special about progressive JPEG, but for normal JPEG there's no need to worry.
posted by Nelson at 8:38 PM on April 22, 2005

JPEGCrop can apparently do this. It can also do a lot of other fun lossless operations on JPEG files.
posted by neckro23 at 10:13 PM on April 22, 2005

In addition to the other tools mentioned, you should be able to do it with JPEGWizard, which lets you do all sorts of manipulations on JPEGs by working with the compressed data to minimize loss.

I'm not too fond of the results of recompressing JPEGs in most cases, but I don't think recompressing progressive is going to be any different that recompressing baseline JPEGs.

Does anyone know if Picasa does compression-domain transforms?
posted by Good Brain at 9:08 AM on April 23, 2005

You can probably use Graphic Converter for OS X. It is a very useful tool.
posted by yesno at 9:02 PM on April 23, 2005