Does this mean that an image that is missing the JFIF "wrapper" can have that wrapper added via the ExifTool?
The reason I ask is that we use an AP Preserver to store thousands (about 250,000) of images. When the AP ingests them it removes the JFIF wrapper so that they are no longer recognizable as image files. This makes it so that we are required to use their interface to get at the imagery in our holdings. It is possible to get at the image files, but only Photoshop is able to open them due to the missing JFIF info. Once the files are open in Photoshop, we can do a "Save As JPEG" and the file will be saved with the JFIF info intact, but that means batching 250,000+ images through the Photoshop process.
It would be nice to be able to write the JFIF info to the files via a command line utility so that we are not dependent on an application that is no longer supported (AP Preserver) or one that is so expensive (Photoshop) to get at our imagery.