"Remove double orientation tags and reset them"

[Allen Huffman]

Greetings, all. I have had an ongoing issue with photos on my Mac where the thumbnail would appear rotated, and when I went to rotate them back, the new image would be wrong. It would take several rotates before I finally got it working again. A minor, but nerve-racking, issue. A few weeks ago, I finally did a web search to try to find out what was causing this. I assumed some internal JPEG thumbnail was just not matching the image orientation, and thought there might be a simple fix through GraphicConverter. I ended up finding one blog post from 2004 that shed some light on this: http://tech.kateva.org/2004/10/graphicc ... -os-x.html That post explained a bug in Image Capture that would double orientation tags, and a GC update in 2004 added the ability to fix this. I have thousands of photos possibly effected by this old Apple bug, and GC crashes (looks like a memory leak) if I start it processing on my top level photo directories. I have been able to limp through by restarting after each sub-sub-sub-folder, and that seems to work. But I notice some file size differences, and that it seems to touch "all" photos. So I wonder: What is this actually doing to my JPEG photo files? Should it even be touching/rewriting files that do not contain the extra information? It seems it doesn't -- some folders come back lightning fast and others churn for a long time. (Perhaps some folders that are quick, just contain few photos.) Anyone know the internals? Thanks, much.