The CAPI interface for programming ISDN hardware expects and gives
faxes in the "Structured Fax File" (SFF) format.

SffToBmp is a converter tool, written in C++, to transform SFF files to
BMP, JPEG or multipage TIFF format. In addition generation of PBM files
(Portable Bitmap) is also possible which can be transformed into nearby
all other graphics formats using the PBMPLUS tools that are included in
almost every Linux distribution nowadays.