It appears that Gimp v2.0 provides the ammunition for the same “nasty tricks (NSFW)”:http://wizbangblog.com/archives/000491.php that allowed so many Tech TVers to drool over nude photos of the lovely “Cat Schwartz”:http://www.catschwartz.com/.
Here’s the gist of it. Most modern digital cameras and photo-editing software will store a thumbnail of the image in the EXIF headers of a JPEG image. EXIF headers are used to store all sorts of nifty image information like focal length, shutter speed, aperture, and camera type. Placing the thumbnail in this header allows it to be obtained and displayed faster and easier because the computer doesn’t have to build a thumbnail from the large version each time it is requested. Unfortunately, if you edit the image and don’t edit the thumbnail inside the EXIF header, a geek with a little know-how can still obtain the original version of the photograph before the editing took place.
“The Gimp”:http://www.gimp.org was never affected before now for one reason. It didn’t save EXIF information at all. So, after editing an image in the Gimp all of the EXIF information was lost, including the thumbnail. Now, however, by default, the JPEG File plugin in the Gimp supports retaining the EXIF information. This includes the unedited version of the thumbnail. It’s not really a bug, it’s just a feature that doesn’t exist. It’s just a matter of knowing what is happening and why. The Gimp doesn’t have any clue about what to do with EXIF information. It only knows how to retain it. Therefore, it is indeed retained, as it states it will do. It is your loss if you don’t realize that that may also mean retaining a version of the image that you wish others wouldn’t see.
Luckily for me, I realized this the easy way. Since none of the image editing software I use on a regular basis supports reading the EXIF thumbnail, I forgot it was even there. Additionally, I rarely edit an image so heavily that a thumbnailed version of it doesn’t appear almost identical to the version I edited. So, unless I’m really looking for it, I’d have no reason to notice that the thumbnail didn’t exactly match the image. However, the other day I had reason to edit an image heavily (it was part of an anniversary gift for Jess). I went to Wal-Mart to print the final image and, apparently, Wal-Marts digital print computer supports reading the EXIF thumbnail. As it displayed thumbnails of all the images on my card for me to choose which ones I wanted printed I got scared thinking that I put the unedited version of the image on the card. Then I remembered poor Cat Schwartz and asked the photo computer to let me see the full image. And there they were, my edits, as I had intended.
If you use Linux, you can use “jhead”;http://www.sentex.net/~mwandel/jhead/ to remove (or view!!) the thumbnails trapped in your images (or the images or others!!). If you’re running Windows or MacOS… I’m not sure.
Good luck, and happy thumbnail hunting.