...it's not a GEM file. It's a Pioneer created proprietary format. It a collection of 2000+ bmp files. Take a hex editor and you'll see that. It has to be decoded. We do know there are bmp files in there but they either don't have a header or they're compressed.
At 7 mb, they are DEFINATELY compressed. That is what baffles me, if it is compressed, then it has to be able to be decompressed. I am just baffled at what kind of img file it is.Here is a list of known img file extensions. A few of them can be ruled out, but, There is still a lot:
IMG
ADEX Corporation ChromaGraph Graphics Card Bitmap Graphic
IMG
AutoCAD CAD-Camera (Autodesk, Inc.)
IMG
Img Software Set Bitmap
IMG
Bitmap Graphic
IMG
Alias Bitmap Graphic
IMG
CloneCD Image (SlySoft Inc.)
IMG
Grand Theft Auto III File (Rockstar Games)
IMG
Disk Copy, ShrinkWrap Disk Image
IMG
ERDAS IMAGINE Image Format (Leica Geosystems , LLC)
IMG
Apple Macintosh Disk Copy Format (Apple Inc.)
IMG
Vicar
IMG
Grand Theft Auto III .DFF and .TXD Archive (Rockstar Games)
IMG
Idrisi32 Raster Image
IMG
Ventura Publisher/GEM VDI Image Format Bitmap
IMG
Image Whatnot / Erdas Imagine MIS / Radiance / Starbase
IMG
Microtek Eyestar
IMG
Planetary Data System
IMG
Starbase
IMG
Sharp GPB
IMG
Radiance Scene Description Image
IMG
Vivid Ray-tracer
IMG
All Image Raw Image (Towodo Software)
IMG
Garmin Basemap (Garmin Ltd.)
IMG
QEMU Qcow Disk Image (Fabrice Bellard)