Reworking a JPEG image

[tedster]

As much as I try to save image source files, there are always situations where an existing jpeg needs to be reworked and there's no hi-res version of the image to be had. I have two tips to share - and I'm hoping for a few more.

1. FLIPPING
There's a small program called the JPEG Wizard which has come to my rescue in several situations - especially when an existing jpg needs to be flipped, but not otherwise edited. The challenge here is that most programs will first decompress the image, then allow editing, and then, finally, RE-compress.

But that method amplifies compression artifacts. It can require you to make a poor tradeoff between a larger file size or case of image acne. A simple flip does not REALLY require a second compression, and JPEG Wizard provides exactly that service. It used to be freeware, but I believe there's now a small fee.

A related issue to this one - can anyone tell if Adobe's ImageReady (the Photoshop companion program) gets this one right in the latest version?

2. FURTHER EDITING
Here's where I'd really appreciate some tips. The first thing I usually do is run Photoshop's DESPECKLE filter. I decide whether that works for me visually or not, and then, either way, I proceed to hand edit.

I usually go up to viewing at 200% or higher, and then look for the compression artifacts around any strong edges. Then I manually replace those spots with the obvious color.

When I've dealt with the visible blebs and blemishes I finally can move ahead with my edit and recompression of the jpeg.

Does anyone have another technique that helps in these awkward situations?

[WebManager]

The "Gifbot" at NetMechanic.com is an excellent - and totally free - online resource for image optimisation.

[mivox]

I usually go up to viewing at 200% or higher, and then look for the compression artifacts around any strong edges. Then I manually replace those spots with the obvious color.

I've yet to find an automated trick that beats PS's blur tool, or (in severe cases) a little eyedropper/semi-transparent paintbrush work for things like this... although I usually zoom in to 400% and lean up close to the monitor. Could just be my eyesight though. ;)

[sun818]

1. FLIPPING

Microsoft PhotoEditor that comes with Office 97/2000 can also rotate images without degrading the quality of the JPEG. I can process dozens of digital images quickly using the keyboard shortcuts I memorized.

[andreasfriedrich]

If you are running GNU/Linux you probably have jpegtran which lets you flip and rotate JPEGs losslessly. You can get the source code from the Independent JPEG Group [ijg.org].

There is just no way to restore the information that were lost when the image was compressed automatically. Manually editing the image and removing artifacts is the only way I know of.

BTW ImageMagick [imagemagick.org] is a great suite of commandline utilities to manipulate images as well.

Andreas