2001.03.31 02:35 "RE: RLE compression", by Gavin Gee
Packbits is definitely in this category. However, if you mean "run length encoding" in a generic sense, CCITTFAX Huffman RLE (K=0), G3 (K>=1) & G4 (K<0) do have encoded horizontal runs of white & black pixels internally. The bits used to represent the runs, however, is completely different. The TIFF spec has details on how the horizontal runs are encoded if you're interested.
From: Daniel McCoy [mailto:firstname.lastname@example.org]
Sent: Friday, March 30, 2001 8:58 AM
To: tiff; Raphael MARC
Subject: Re: RLE compression