IMG (file format): Difference between revisions

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IMG file format may refer to several different and incompatible file formats, which usually just have the use of the .img file extension in common:

Binary files used to store raw disk images of floppy disks or hard drives.
The Apple Disk Image proprietary disk image file format, used by Apple Disk Copy for Mac OS.
Garmin's map file format, used by Garmin GPS devices.
The GEM Raster file format, an image file format used to store bitmap digital images on the Graphical Environment Manager operating environment. Used by the GEM Paint software.
Other digital image file formats used by different graphics software packages (such as ERDAS IMAGINE).

This article will focus on the first format indicated above, raw disk image files that use the .img extension.

IMG raw disk image format

The .img file extension is used by files which contain raw dumps of a disk, commonly called disk images. Since a raw image consists of a sector-by-sector binary copy of the source medium, the actual format of the file contents will depend on the file system of the disk from which the image was created. A similar file extension, .ima, is used by some tools to refer to the same type of raw disk image files.

The .img file extension was originally associated to floppy disk raw disk images only, though it is currently used to refer to hard drive disk images as well.

A variant of the format is called IMZ, and consists of a gzipped version of a raw disk image. These files use the .imz file extension, and are commonly found in compressed images of floppy disks.

The file size of a raw floppy disk image will always be a multiple of the sector size — generally 512 bytes, but other sizes such as 128 and 1024 exist. More precisely the file size corresponds to Cylinders×Heads×(Sectors per track), e.g., 1440KB=80×2×18×512 for 80 cylinders (tracks) and 2 heads (sides) with 18 sectors per track. A typical raw disk image of a floppy disk begins with a FAT boot sector, where the first byte is normally hexadecimal EB (code for a 8bit short jump, offset in the 2nd byte) with third byte 90 (code for a NOP), or rarely EA (code for a 16bit jump, offset in 2nd and 3rd byte).

Raw disk images of optical media (such as CDs and DVDs) are usually referred to as ISO images, and use the .iso file extension. Functionally, however, they are equivalent to IMG files, though their internal format follows the structure of an optical media file system such as ISO 9660 (for CDs) or UDF (for DVDs).

Tools

The raw IMG file format is used by several tools:

Tools such as RaWrite and WinImage use the IMG disk image format to read and write floppy disk images.
Programs such as ImDisk and Virtual Floppy Drive can mount a raw image of a floppy disk to emulate a floppy drive under Microsoft Windows.
Nero Burning ROM supports reading IMG files for creating bootable CDs.
mtools allows manipulation of MS-DOS floppy disk images in Unix systems.
Programs such as dsktrans from the LibDsk suite of command-line tools (available for for Linux, MS-DOS, and Microsoft Windows) will convert between different raw disk image formats.
dd can be used in Linux to create raw disk image files of disks.
Qemu uses IMG files as its default format for hard drive disk images.

References

v t e Disk image file formats
Comparison of disc image software
Optical discs	BIN+CUE DAA IMG+CCD+SUB ISO ISZ MDF+MDS MDX NRG UIF
Hard disks	DMG FVD IMG ISO NDIF QCOW UDIF VDI VHD VMDK WIM
Floppy disks	ADF, ADZ DC42, DART DMS IMG, IMA, IMZ VFD
CDDA	Disc Description Protocol
Convention: Any item in this table that has the form of "A+B" or "A+B+C" indicates a disk format that spans multiple files, where A contains the bulk of the data, and B and C are sidecar files.

Categories:

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	'''IMG file format''' may refer to several different and incompatible file ~~formats~~, which usually just have the use of the ''.img'' ] in common:		'''IMG file format''' may refer to several different and incompatible ]s, which usually just have the use of the ''.img'' ] in common:

	* Binary ~~files~~ used to store raw ] of ]s or ]s.		* ]s used to store raw ] of ]s or ]s.
	* The ] proprietary ] file format, used by ] for ].		* The ] proprietary ] file format, used by ] for ].
	* ], used by ] GPS devices.		* ], used by ] GPS devices.
Line 7:		Line 7:
	* Other ] file formats used by different graphics software packages (such as ERDAS IMAGINE).		* Other ] file formats used by different graphics software packages (such as ERDAS IMAGINE).

	This article will focus on the first format indicated above, raw disk image files that use the ~~extension~~ ''.img''.		This article will focus on the first format indicated above, raw disk image files that use the ''.img'' extension.

	==IMG raw disk image format==		==IMG raw disk image format==
	The ''.img'' ] is used by files which contain raw dumps of a disk, commonly called ]s. Since a raw image consists of a ]-by-sector binary copy of the source medium, the actual format of the file contents will depend on the ] from which the ~~raw disk~~ image was created. A similar file extension, ''.ima'', is used to refer to the same type of raw disk image files ~~by some tools~~.		The ''.img'' ] is used by files which contain raw dumps of a ], commonly called ]s. Since a raw image consists of a ]-by-sector binary copy of the source medium, the actual format of the file contents will depend on the ] of the disk from which the image was created. A similar file extension, ''.ima'', is used by some tools to refer to the same type of raw disk image files.

	The ''.img'' file extension was originally associated to ] raw disk images only, though it ~~was~~ ~~later~~ used to refer to ] disk images as well.		The ''.img'' file extension was originally associated to ] raw disk images only, though it is currently used to refer to ] disk images as well.

	A variant of the format is called IMZ, and consists of a ]ped version of a raw ~~IMG~~ disk image. These files use the ''.imz'' file extension, and are commonly found in compressed images of floppy disks.		A variant of the format is called IMZ, and consists of a ]ped version of a raw disk image. These files use the ''.imz'' file extension, and are commonly found in compressed images of floppy disks.

	A ~~typical~~ raw floppy disk image begins with a ], where the first byte is normally hexadecimal EB (code for a 8bit short jump, offset in the 2nd byte) with third byte 90 (code for a NOP), or rarely EA (code for a 16bit jump, offset in 2nd and 3rd byte). The file size will always be a multiple of the sector size — generally 512 bytes, but other sizes such as 128 and 1024 ~~existed~~. More precisely the file size corresponds to <tt><abbr title="CHS">Cylinders×Heads×(Sectors per track)</abbr></tt>, e.g., <tt>1440KB=80×2×18×512</tt> for 80 cylinders (tracks) and 2 heads (sides) with 18 sectors per track.		The file size of a raw floppy disk image will always be a multiple of the sector size — generally 512 bytes, but other sizes such as 128 and 1024 exist. More precisely the file size corresponds to <tt><abbr title="CHS">Cylinders×Heads×(Sectors per track)</abbr></tt>, e.g., <tt>1440KB=80×2×18×512</tt> for 80 cylinders (tracks) and 2 heads (sides) with 18 sectors per track. A typical raw disk image of a floppy disk begins with a ], where the first byte is normally hexadecimal EB (code for a 8bit short jump, offset in the 2nd byte) with third byte 90 (code for a NOP), or rarely EA (code for a 16bit jump, offset in 2nd and 3rd byte).

	Raw disk images of optical media (such as ]s and ]s) are usually referred to as ]s, and use the ''.iso'' file extension. Functionally, however, they are equivalent to IMG files, though their internal format follows the structure of an optical media file system such as ].		Raw disk images of optical media (such as ]s and ]s) are usually referred to as ]s, and use the ''.iso'' file extension. Functionally, however, they are equivalent to IMG files, though their internal format follows the structure of an optical media file system such as ] (for CDs) or ] (for DVDs).

	===Tools===		===Tools===
	The raw IMG file format is used by several tools:		The raw IMG file format is used by several tools:
	* Tools such as RaWrite and ] use the IMG disk image format to read and write floppy disk images.		* Tools such as RaWrite and ] use the IMG disk image format to read and write floppy disk images.
	* Programs such as ] and can mount a raw image of a floppy disk to emulate a floppy drive under Windows.		* Programs such as ] and can mount a raw image of a floppy disk to emulate a floppy drive under ].
	* ] allows manipulation of ] floppy disk images in ] systems.
	* ] supports reading IMG files for creating ]s.		* ] supports reading IMG files for creating ]s.
	* ] ~~uses~~ it as ~~its~~ ~~default~~ ~~format~~ ~~for~~ ] ~~disk images~~.		* ] allows manipulation of ] floppy disk images in ] systems.
	* Programs such as ''dsktrans'' from the ''LibDsk''<ref></ref> suite of command-line tools ~~will~~ ~~convert between raw disk image formats,~~ for ], ], and ].		* Programs such as ''dsktrans'' from the ''LibDsk''<ref></ref> suite of command-line tools (available for for ], ], and ]) will convert between different raw disk image formats.
	* ] can be used in ] to create raw disk image files of disks.		* ] can be used in ] to create raw disk image files of disks.
			* ] uses IMG files as its default format for ] disk images.

	==References==		==References==