ILBM
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Overview
ILBM (or IFF-ILBM, or LBM) is a raster image file format, based on the IFF container format. ILBM stands for InterLeaved BitMap.
Identification
The ASCII strings "FORM", "ILBM", and "BMHD" appear near the beginning of the file.
Disambiguation
We are tentatively defining "ILBM" files to be exactly those IFF files which contain an ILBM chunk. However, that may not be the best way to categorize IFF image files.
There are other IFF image formats that don't use an ILBM chunk, such as PBM, RGBN, and RGB8. Sometimes these formats are still considered to be "ILBM".
And conversely, there are formats like HAM, which do use an ILBM chunk, but may have little else in common with plain vanilla ILBM images.
Special types of ILBM
HAM
HAM images are designed to work with the Amiga's Hold-And-Modify display mode. HAM files should contain a "CAMG" chunk with a particular flag set. Images have a maximum of 4096 colors.
HAM8
HAM8 is a variant of HAM, designed to work with a display mode available on some Amigas. Images have a maximum of 262,144 colors.
HALFBRITE
HAM images are designed to work with the Amiga's Halfbrite display mode. HALFBRITE files should contain a "CAMG" chunk with a particular flag set. Images have a maximum of 64 colors.
See also
- IFF-PBM (Planar BitMap)
