Gemc
Prepare your CD images (BIN,CDI,NRG,CCD or similar) for compression
...Compress the ECM file (i.e. filename.bin.ecm) using your favorite compression program (i.e. 7Z,RAR,ZIP..).
Back up, transmit via Internet, or whatever you normally do with CD images!
When you want to burn the CD again, extract the original CD image from the ECM file.
space saved depends on the number of sectors with unnecessary EDC/ECC data in them, which will depend on the specific type of CD