The JPEG photo format is great because the resulting images have a reduced filesize, but it is often at the expense of the image quality. There are varying levels of JPEG compression, some of which are noticeably horrible while others are pretty good. The result of poor JPEG compression is often blotchiness and "artifacts".
There is a free program called the JPEG Enhancer that will reduce some of the bad portions of an image, but I couldn’t let this program go by untested. I quickly installed it and looked for an image that I could purposely compress to reduce the image quality. I used one that I took of a cruise ship and cropped it out to contain the ship’s name. The reason I did this is that text often brings out the worst in JPEG compression, and as expected the result wasn’t very good (I did turn the quality down as low as I could though).
On the left side of the application you’ll see the original image, and on the right side is the "enhanced" version. The images are also zoomed in so that you can see the compression a little easier:
This program actually surprised me by doing a much better job than I had expected. All I had to do was play with the sliders on the bottom and hit the Process button to have it analyze the entire image with the desired settings. It even removed some of the defects that were originally on the ship’s paneling.
The only bad thing about the program is that it removes some of the crispness that the photo originally had, but the application is free so I can’t really complain. I do have some old photos from my original digital camera that I might run through here to see if it can clean up the poor JPEG compression. :)