rdjpgcom - display text comments from a JPEG file


   rdjpgcom [ -raw ] [ -verbose ] [ filename ]


   rdjpgcom  reads  the  named JPEG/JFIF file, or the standard input if no
   file is named, and prints any text comments found in the  file  on  the
   standard output.

   The  JPEG standard allows "comment" (COM) blocks to occur within a JPEG
   file.  Although the standard doesn't actually define  what  COM  blocks
   are for, they are widely used to hold user-supplied text strings.  This
   lets you add annotations, titles, index terms, etc to your JPEG  files,
   and  later retrieve them as text.  COM blocks do not interfere with the
   image stored in the JPEG file.  The maximum size of a COM block is 64K,
   but you can have as many of them as you like in one JPEG file.


   -raw   Normally  rdjpgcom escapes non-printable characters in comments,
          for security reasons.  This option avoids that.

   -verbose Causes rdjpgcom to also display the JPEG image dimensions.

   Switch names may be abbreviated, and are not case sensitive.


   rdjpgcom does not depend on the IJG JPEG library.  Its source  code  is
   intended  as  an illustration of the minimum amount of code required to
   parse a JPEG file header correctly.

   In -verbose mode, rdjpgcom will also attempt to print the  contents  of
   any  "APP12"  markers  as  text.   Some  digital  cameras produce APP12
   markers containing useful textual information.  If you  like,  you  can
   modify the source code to print other APPn marker types as well.


   cjpeg(1), djpeg(1), jpegtran(1), wrjpgcom(1)


   Independent JPEG Group

                             02 April 2009                     RDJPGCOM(1)


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