1 unstable release

0.1.0 Nov 23, 2020

#2936 in Parser implementations

22 downloads per month
Used in pdf-create

MPL-2.0 license



This crate aims to implement the T.4 and T.6 standard of the ITU’s Telecommunication Standardization Sector (ITU-T). These documents decribe a family of encoding/decoding algorithms for monochrome i.e. black-and-white bitmaps, which have been created for fax machines.

They are also used in the Adobe PDF file format for the encoding of monochrome bitmap images as the /CCITTFaxDecode stream filter.

State of implementation

This crate currently implements an Encoder and a Decoder for the Group 4 2D coding scheme specified in T.6. This is sufficient for creating PDF documents that use CCITTFaxDecode to draw Type3 font glyphs. If you want to support non-negative values of the K decode parameter, i.e. Group 3 encoding, feel free to submit a Pull Request.


CCITT fax encodings


~18K SLoC