PDF glossary
JBIG2 and CCITT
Compression formats for black and white images, used by document scanners to make tiny files.
CCITT Group 4 is the fax era standard; JBIG2 is more efficient and can reuse symbol shapes across a page.
Lossy JBIG2 has been known to swap similar looking digits, which is why lossless modes are safer for documents with numbers.
Related terms