Mac下有一个自带的工具可以完成这个事情，命 令如下hdiutil
hdiutil convert: convert an image into a different format
Usage: hdiutil convert -format <format> -o <outfile> <image>
Image Formats:
UDRO - read-only
UDCO - compressed (ADC)
UDZO - compressed
UDBZ - compressed (bzip2)
ULFO - compressed (lzfse)
UFBI - entire device
IPOD - iPod image
UDxx - UDIF stub
UDSB - sparsebundle
UDSP - sparse
UDRW - read/write
UDTO - DVD/CD master
DC42 - Disk Copy 4.2
RdWr - NDIF read/write
Rdxx - NDIF read-only
ROCo - NDIF compressed
Rken - NDIF compressed (KenCode)
Convert options:
-ov overwrite target file(s) if it already exists
-align [<sector alignment>] [4 aka 2K]
-pmap
-segmentSize < ?? | ??b | ??k | ??m | ??g | ??t | ??p | ??e >
(blocks, bytes, kilobytes, megabytes, gigabytes, terabytes, petabytes, exabytes)
-tasks <task count> [8]
Common options:
-encryption <crypto method>
AES-128 - 128-bit AES encryption (recommended)
AES-256 - 256-bit AES encryption (more secure, but slower)
-stdinpass
-agentpass
-certificate <path-to-cert-file>
-srcimagekey <key>=<value> (-imagekey is a synonym)
-tgtimagekey <key>=<value>
-shadow <shadowfile>
-insecurehttp
-cacert <file | dir>
-plist
-puppetstrings
-verbose
-debug
-quiet
例：
hdiutil convert -format UDTO -o OSX.iso Install.OS.X.El.Capitan.app.10.11.dmg