jbig2dec

This is a mirror: the canonical repo is: git.ghostscript.com/jbig2dec.git. This repo does not host releases, they are here: https://github.com/ArtifexSoftware/jbig2dec/tags (by ArtifexSoftware)

Jbig2dec Alternatives

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jbig2dec reviews and mentions

Posts with mentions or reviews of jbig2dec. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2024-04-22.
  • Ask HN: What rabbit hole(s) did you dive into recently?
    12 projects | news.ycombinator.com | 22 Apr 2024
    > The worst offender (so far) is the JBIG2 format (several major libraries, including jbig2dec), a very popular format that gets EXTREMELY high compression ratios on bilevel images of types typical to scanned pdfs. But: it's also a format that's pretty slow to decompress—not something you want in a UI loop, like a PDF reader is! And, there's no way around that—if you look at the hot loop, which is arithmetic coding, it's a mess of highly branchy code that's purely serial and cannot be thread- nor SIMD- parallelized.

    Looking at the jbig2dec code, there appears to be some room for improvement. If my observations are correct, each segment has its own arithmetic decoder state, and thus can be decoded in its own thread. The main reader loop[1] is basically a state machine which attempts to load each segment in sequence[2], but it should not need to. The file has segment headers which contains the segments offsets and sizes. It should be possible to first read this header, then spawn N-threads to decode N-segment in parallel. Obviously, you don't want the threads competing for the file resource, so you could load each segment into its own buffer first, or mmap the whole file into memory.

    [1]:https://github.com/ArtifexSoftware/jbig2dec/blob/master/jbig...

    [2]:https://github.com/ArtifexSoftware/jbig2dec/blob/master/jbig...

  • MuPDF WASM Viewer Demo
    9 projects | news.ycombinator.com | 20 Apr 2024
    I still haven't found an tolerably fast PDF reader, and I'm permanently miserable with that file format. The example in OP works great, but that's only an "easy, modern" PDF made up of text. There's still nothing adequate (mupdf/mutool included) for the common case of scanned-page PDF's.

    The root problem isn't an easy performance fix: it's that a very popular PDF image compression format, JBIG2 [0], is unlike modern formats slow in decompression as well as compression. Here's the decompress hot loop [1,2] from libjbig2dec.so, which MuPDF calls out to. I isn't thread- or SIMD- parallelized, and I suspect that it isn't possible at all. There's just no easy way forwards in the near future—other than "buy faster CPU's".

    [0] https://en.wikipedia.org/wiki/JBIG2

    [1] https://github.com/ArtifexSoftware/jbig2dec/blob/master/jbig...

    [2] https://github.com/ArtifexSoftware/jbig2dec/blob/master/jbig...

Stats

Basic jbig2dec repo stats
2
35
2.8
about 1 month ago

ArtifexSoftware/jbig2dec is an open source project licensed under GNU General Public License v3.0 or later which is an OSI approved license.

The primary programming language of jbig2dec is C.


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