** Changed in: libjpeg6b (Debian)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/381140

Title:
  jpegtran is NOT lossless with metadata (Exif data, etc.) by default

Status in “libjpeg6b” package in Ubuntu:
  Confirmed
Status in “libjpeg6b” package in Debian:
  Fix Released

Bug description:
  From the man page:
          NAME
                 jpegtran - lossless transformation of JPEG files
          ...
                 ... But by the same token, jpegtran cannot perform lossy 
operations
                 such as changing the image quality.
          ...
                 -copy comments
                        Copy only comment markers.  This setting  copies  
comments  from
                        the source file, but discards any other inessential 
data.
          
                 -copy all
                        Copy  all  extra  markers.  This setting preserves 
miscellaneous
                        markers found in the source file, such as Exif data, 
JFIF thumb‐
                        nails and Photoshop settings.  In some files these 
extra markers
                        can be sizable.
          
                        The default behavior is -copy comments.

  As you can see, jpegtran explicitly claims to be lossless. It even
  further claims it "cannot perform lossy operations". (I realize now
  that's only talking about image data.) But, the default for extra marker
  copying is "-copy comment", which drops Exif data. This means that every
  picture I've rotated with jpegtran has lost its Exif data. Luckily, I
  probably don't need it that bad, but I was using this tool explicitly
  because it's supposedly lossless.

  I realize that the man page is clear about the default value of -copy,
  but who reads an entire man page to find the one option that makes the
  description under NAME untrue?

  I propose these possible solutions, in order of preference:
       1. Add a new argument to copy that behaves like -copy all, but
          *updates* the JFIF and/or EXIF thumbnails after transforming
          the image. Make this option the default.
       2. Add a new argument to copy that behaves like -copy all, but
          *drops* (does not copy) the JFIF thumbnails. Make this option
          the default.
       3. Make -copy all the default.
       4. Add a new argument to copy that behaves like -copy comments, but
          also copies exif markers. Make this option the default. The
          first patch here might be useful, though I'm not sure if it also
          copies comments:
          https://bugzilla.redhat.com/show_bug.cgi?id=106060
       5. Add an asterisk after lossless at the top of the man page and
          then add a note under it such as, '* The only extra markers
          copied by default are comments. This means certain data (Exif
          data, JFIF thumbnails, Photoshop settings, etc.) will be lost.
          To copy all extra markers, see the "-copy all" argument.'

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