[Bug 1992228] Re: Fax/PDF performance regression compared to focal

[Julian Andres Klode]

** Also affects: imagemagick (Ubuntu Kinetic)
   Importance: Undecided
       Status: New

** Also affects: imagemagick (Ubuntu Jammy)
   Importance: Undecided
       Status: New

** Changed in: imagemagick (Ubuntu Jammy)
       Status: New => Triaged

** Changed in: imagemagick (Ubuntu Kinetic)
       Status: New => Triaged

** Changed in: imagemagick (Ubuntu Jammy)
   Importance: Undecided => Medium

** Changed in: imagemagick (Ubuntu Kinetic)
   Importance: Undecided => High

** Changed in: imagemagick (Ubuntu Jammy)
   Importance: Medium => High

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https://bugs.launchpad.net/bugs/1992228

Title:
  Fax/PDF performance regression compared to focal

Status in imagemagick package in Ubuntu:
  Triaged
Status in imagemagick source package in Jammy:
  Triaged
Status in imagemagick source package in Kinetic:
  Triaged

Bug description:
  I'm regularly using `convert` to turn a line-art PNM file to a PDF
  with Fax/Group4 compression.

  This used to take a few seconds on focal.

  I updated to jammy and it takes almost 5 minutes now!

  
  $ time convert -verbose scan.pnm -compress Fax scan.pdf
  scan.pnm PBM 5120x7138 5120x7138+0+0 1-bit Bilevel Gray 4.35672MiB 0.610u 0:00.487
  scan.pnm=> GROUP4 5120x7138 5120x7138+0+0 1-bit Gray 124981B 284.590u 4:43.594
  scan.pnm=> GROUP4 5120x7138=>76x106 76x106+0+0 1-bit Gray 242B 0.150u 0:00.134
  scan.pnm=>scan.pdf PBM 5120x7138 5120x7138+0+0 1-bit Bilevel Gray 127042B 285.280u 4:44.267

  real	4m44.795s
  user	2m5.962s
  sys	2m39.970s

  
  Input image here: https://stephan.walter.name/files/scan.pnm

  I tried to reproduce the issue with upstream
  https://github.com/ImageMagick/ImageMagick6 , but the PDF file
  generated was just noise - I'm probably missing some `configure`
  options or libraries.

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