DiskImageMounter

DiskImageMounter is the utility that handles mounting disk volume images in Mac OS X, starting with version 10.3. DiskImageMounter works by either launching a daemon to handle the disk image or by contacting a running dæmon and have it mount the disk. 
Like BOMArchiveHelper, DiskImageMounter has no GUI when double-clicked; doing so does nothing. The only GUI the program ever displays is a window with a progress bar and mount options (cancel or skip verification) or an error report if it could not mount the image. It is found in /System/Library/CoreServices/DiskImageMounter.app.
Starting with version 10.7, Apple "removed double-click support for images using legacy metadata." DiskImageMounter will not be able to open .img (NDIF only), .smi (self mounting), .dc42 (Disk Copy 4.2), and .dart (DART) disk image formats that was previously supported in version 10.6 and earlier.
Image formats supported.
DiskImageMounter supports a variety of disk image file types:
As of macOS 11.0, support for the following formats has been removed: