[Pkg-gmagick-im-team] Bug#1006441: imagemagick-6.q16: multiline comments are not idempotent in pgm codec

[Mathieu Malaterre]

Package: imagemagick-6.q16
Version: 8:6.9.11.60+dfsg-1.3
Severity: normal

Dear Maintainer,

I cannot do a round-trip operation pgm -> jpg -> pgm while preserving
multilines comments.

Steps:

% convert -comment 'hello\nworld\n!' -depth 8 -size 8x8 xc:black black.pgm
% convert black.pgm black.jpg
% convert black.jpg idem.pgm
% head black.pgm idem.pgm
==> black.pgm <==
P5
#hello
#world
#!
8 8
255

==> idem.pgm <==
P5
#hello
#world
#!
#
8 8
255

-- Package-specific info:
ImageMagick program version
---------------------------
animate:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
compare:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
convert:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
composite:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
conjure:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
display:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
identify:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
import:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
mogrify:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
montage:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org
stream:  ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org

-- System Information:
Debian Release: 11.2
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable-debug'), (500, 'proposed-updates-debug'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.15.0-0.bpo.3-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages imagemagick-6.q16 depends on:
ii  hicolor-icon-theme     0.17-2
ii  libc6                  2.31-13+deb11u2
ii  libmagickcore-6.q16-6  8:6.9.11.60+dfsg-1.3
ii  libmagickwand-6.q16-6  8:6.9.11.60+dfsg-1.3

Versions of packages imagemagick-6.q16 recommends:
ii  ghostscript                  9.53.3~dfsg-7+deb11u2
pn  libmagickcore-6.q16-6-extra  <none>
pn  netpbm                       <none>

Versions of packages imagemagick-6.q16 suggests:
pn  autotrace                            <none>
pn  cups-bsd | lpr | lprng               <none>
ii  curl                                 7.74.0-1.3+deb11u1
pn  enscript                             <none>
ii  ffmpeg                               7:4.3.3-0+deb11u1
ii  gimp                                 2.10.22-4
pn  gnuplot                              <none>
pn  grads                                <none>
pn  graphviz                             <none>
ii  groff-base                           1.22.4-6
pn  hp2xx                                <none>
pn  html2ps                              <none>
pn  imagemagick-doc                      <none>
pn  libwmf-bin                           <none>
pn  mplayer                              <none>
pn  povray                               <none>
pn  radiance                             <none>
ii  sane-utils                           1.0.31-4.1
ii  texlive-binaries [texlive-base-bin]  2020.20200327.54578-7
pn  transfig                             <none>
pn  ufraw-batch                          <none>
ii  xdg-utils                            1.1.3-4.1

-- no debconf information