Keith Packard wrote on 2002-03-08 00:09 UTC:
> I was hoping we'd find a simple compression technique that could yield 
> a value for 'f' of less than one; certainly the regularity of the data 
> leads one to believe that it is possible.

Candidates:

  - ITU's Group 4 fax compression
    simple, widely used, but optimized for FAX resolutions (fixed
    huffman table)

  - ITU's JBIG
    somewhat more complicated (but public domain implementations
    readily available), adaptive model, therefore resolution independent,
    unfortunately based on IBM's arithmetic coder patents

  - W3C's PNG
    another lossless image compression algorithm. Unlike the others, not
    exactly optimized for glyph compression, but also reasonably good.
    Has lossy and lossless modes, therefore also good for anti-aliased
    glyphs, not just single bit.

All three standards have lot's of options, only few of which make sense
for font glyph uploading. I think, a profile (subset) of PNG would be a
reasonably good choice. It perhaps just shouldn't be called PNG to avoid
confusion, even though each font stream would remain a fully compliant
PNG file.

PNG uses a simple 2-D predictor followed by gzip.

http://www.w3c.org/Graphics/PNG/

I suggest that you load the PNG spec into an editor, delete everything
that is not useful for font uploading and then have a look whether what
remains sounds usable.

Markus

-- 
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org,  WWW: <http://www.cl.cam.ac.uk/~mgk25/>

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