Case 1: You created the file in the first place, and this file is for the Macintosh platform only.
In this case you could store the ImageDescriptionHandle in a resource, and when you want to decompress the file, read this resource before doing the decompression operation.
Case 2: You read an arbitrary JPEG file generated by any possible platform. The
QuickTime SDK CD has an example of a JFIF translator, JFIF is the interchange
format of JPEG files across computer platforms. Check out the ScanJPEG function
in this sample to see how to scan the file for the image description
information that you could then later use in FDecompressImage.