Comments on: Converting a standard JPEG into a progressive one?

Question: Converting a standard JPEG into a progressive one?

Nikolai — Fri, 22 Apr 2005 18:23:38 -0800

Is it possible to convert a standard JPEG into a progressive one without losing quality? If so, what can I use to do it?

By: fvw

fvw — Fri, 22 Apr 2005 18:40:51 -0800

Yes, it is technically possible. I'm afraid I don't know any software that does it though…

By: slipperywhenwet

slipperywhenwet — Fri, 22 Apr 2005 18:43:38 -0800

Try resaving in photoshop, with the highest image quality.

By: delfuego

delfuego — Fri, 22 Apr 2005 20:32:06 -0800

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.

By: Nelson

Nelson — Fri, 22 Apr 2005 20:38:48 -0800

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.

By: neckro23

neckro23 — Fri, 22 Apr 2005 22:13:42 -0800

JPEGCrop can apparently do this. It can also do a lot of other fun lossless operations on JPEG files.

By: Good Brain

Good Brain — Sat, 23 Apr 2005 09:08:26 -0800

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?

By: yesno

yesno — Sat, 23 Apr 2005 21:02:17 -0800

You can probably use Graphic Converter for OS X. It is a very useful tool.