You also have to possibility to compress (option -c) the data so the image takes less space on your backup media. If you have used your computer a while the empty space may actually be filled with data from deleted files (since files usually don't get removed, they are just marked as deleted in a file system). That may be difficult to compress efficiently, therefore you are recommended to clear all empty space which can be done by this script (option -z). It currently works and have been tested for ext2, ext3, ext4, FAT and NTFS. Adding other types would be trivial though, since the script only depends on the capabilities of the host system.
As of version 0.2 you can also get the MD5 sum calculated (option -5) on-the-fly for both compressed and non-compressed images.
The script uses the GNU software dd (which comes with all Linux distros) to perform the real work.
Further help on how to use the program and restore an image is written inside the script file.