Convert disk IMG to standard ISO on a Macbook

This will work for an IMG file or DMG. I stumbled on the need for this after creating a DVD on my Macbook and wanting the generated IMG file to be in a standard ISO format. Just use the command line:

// for IMG files.
$ hdiutil convert input.img -format UDTO -o output.iso

// for DMG files.
$ hdiutil convert input.dmg -format UDTO -o output.iso