The Apple Icon Image format is the icon format used in Apple Inc. 's Mac OS X . It supports icons of 16×16, 32×32, 48×48, 128×128, 256×256, 512×512, and 1024×1024 pixels, with both 1- and 8-bit alpha channels and multiple image states (example: open and closed folders). The fixed-size icons can be scaled by the operating system and displayed at any intermediate size.
File structure [ edit ] The file format consists of an 8 byte header, followed by any number of icons.
Offset
Size
Purpose
0
4
Magic literal, must be "icns" (0x69, 0x63, 0x6e, 0x73)
4
4
Length of file, in bytes, msb first
Icon data [ edit ]
Offset
Size
Purpose
0
4
Icon type, see OSType below.
4
4
Length of data, in bytes (including type and length), msb first
8
Variable
Icon data
Compression [ edit ] Over time the format has been improved and there is support for compression of some parts of the pixel data. The 32-bit ("is32", "il32", "ih32","it32") pixel data is often compressed (per channel) with a format similar to PackBits .[ 1]
Icon types [ edit ]
OSType Length (bytes)
Size (pixels)
Supported OS Version
Description
ICON 128
32
1.0
32×32 1-bit mono icon
ICN# 256
32
6.0
32×32 1-bit mono icon with 1-bit mask
icm# 48
16
6.0
16×12 1 bit mono icon with 1-bit mask
icm4 96
16
7.0
16×12 4 bit icon
icm8 192
16
7.0
16×12 8 bit icon
ics# 64 (32 img + 32 mask)
16
6.0
16×16 1-bit mask
ics4 128
16
7.0
16×16 4-bit icon
ics8 256
16
7.0
16x16 8 bit icon
is32 varies (768)
16
8.5
16×16 24-bit icon
s8mk 256
16
8.5
16x16 8-bit mask
icl4 512
32
7.0
32×32 4-bit icon
icl8 1,024
32
7.0
32×32 8-bit icon
il32 varies (3,072)
32
8.5
32x32 24-bit icon
l8mk 1,024
32
8.5
32×32 8-bit mask
ich# 288
48
8.5
48×48 1-bit mask
ich4 1,152
48
8.5
48×48 4-bit icon
ich8 2,304
48
8.5
48×48 8-bit icon
ih32 varies (6,912)
48
8.5
48×48 24-bit icon
h8mk 2,304
48
8.5
48×48 8-bit mask
it32 varies (49,152)
128
10.0
128×128 24-bit icon
t8mk 16,384
128
10.0
128×128 8-bit mask
icp4 varies
16
10.7
16x16 icon in JPEG 2000 or PNG format
icp5 varies
32
10.7
32x32 icon in JPEG 2000 or PNG format
icp6 varies
64
10.7
64x64 icon in JPEG 2000 or PNG format
ic07 varies
128
10.7
128x128 icon in JPEG 2000 or PNG format
ic08 varies
256
10.5
256×256 icon in JPEG 2000 or PNG format
ic09 varies
512
10.5
512×512 icon in JPEG 2000 or PNG format
ic10 varies
1024
10.7
1024×1024 in 10.7 (or 512x512@2x "retina" in 10.8) icon in JPEG 2000 or PNG format
ic11 varies
32
10.8
16x16@2x "retina" icon in JPEG 2000 or PNG format
ic12 varies
64
10.8
32x32@2x "retina" icon in JPEG 2000 or PNG format
ic13 varies
256
10.8
128x128@2x "retina" icon in JPEG 2000 or PNG format
ic14 varies
512
10.8
256x256@2x "retina" icon in JPEG 2000 or PNG format
the values inside the brackets () in the length column is the uncompressed length.
Other types [ edit ]
OSType Length (bytes)
Description
'TOC ' varies
"Table of Contents" a list of all image types in the file, and their sizes (added in Mac OS X 10.7 )
'icnV' 4
4-byte big endian float - equal to the bundle version number of Icon Composer.app that created to icon
See also [ edit ] References [ edit ]
^ Macintosh Icons
External links [ edit ]
Versions
Applications
Utilities
Technology and
