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Re: Trinary image compression

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Willem <willem@turtle.stack.nl> wrote:

(snip, I wrote)
> ) I very much like the idea of JBIG and the compression of binary
> ) (black, white, but no gray or other colors) images.

> ) There are, however, some books, at least computer manuals,
> ) written with two ink colors. (Black and blue for example.)

> ) There is, as far as I know, no JTIG compression for trinary
> ) (black, blue, white) images. (Presumably one could allow for
> ) any three colors, likely one being white.)


(snip)

> I think it would be easiest if you split the image in two,
> one containing the black text and one containing the blue text.

Yes, that is fine. But there are no standard compression algorithms,
more specifically, no popular decompression algorithms, that do it.
(Considering some cases where the decompression algorithm is
specified separately from the many possible compression algorithms
that it supports.)

I suppose one could use LZW on two bit/pixel image files, but that
is likely not near as good as JBIG2 on the two separate images.

There may be use for four or five color, but no shading, in some
image systems. 

The nice thing about JBIG2 is that it has been supported by PDF
for some years now. 

-- glen

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Thread

Trinary image compression glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-10-22 19:22 +0000
  Re: Trinary image compression Willem <willem@turtle.stack.nl> - 2012-10-22 20:53 +0000
    Re: Trinary image compression glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-10-22 23:43 +0000
      Re: Trinary image compression Niels Fröhling <spamtrap@adsignum.com> - 2012-10-22 20:41 -0600
    Re: Trinary image compression Thomas Richter <thor@math.tu-berlin.de> - 2012-10-23 08:39 +0200
      Re: Trinary image compression glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-10-23 06:59 +0000

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