I tried the LEAP plug-in, I couldn't read the JPEG 2000 files on my Mac. Fnord software in San Francisco puts out this free Photoshop plug-in for Mac and PC. Last updated 1/03. Written by Brendan Bolles
The Fnord plug-in uses Kakadu 3.2. QuickTime/Mac and Yahoo Messenger use the same development kit, created by Dr. David Taubman at the University of New South Wales. The common SDK source for this plug-in and QuickTime may be responsible for the Mac compatibility.
I used it with Photoshop Elements 2.0/PC to compress a 10MB PNG map scan to a very readable 200K JP2 file. Unlike the LEAP plug-in the Fnord file was readable by Quicktime/Mac. In both cases I included the Adobe sRGB ICC file, but Quicktime choked on the LEAP generated jp2 file.