The Fuzzy BitMap tools.  (Adapted directly from the FreeBSD Ports
system.)

This package provides a set of UNIX filter commands which perform
image-processing steps, and can read and write multiple formats.
A NOP filter, fbcat, can be used to perform format conversions.  Similar
to netpbm or urt.  The key reason that I wanted fbm is because fbm can
deal with IFF FORM ILBM files, while other tools at my disposal cannot.

Two caveats:

I left in FreeBSD patches that keep fbm from using standard graphics
libraries.  If, like me, you only use fbm to import an odd file or two,
then uninstall, then you might appreciate not needing to install
various graphics libraries.

There seems to be some buggy code for emitting ILBM's.  IFF requires
that all chunks be padded to 16-bit boundaries; this also applies to
each scanline of each bitplane in FORM ILBM.  It appears that fbcat
(at least) fails to properly handle this padding on at least one
case of reading or writing ILBM files.  (This isn't a problem if
the ILBM width is a multiple of 16.)