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RDJPGCOM(1)                                                        RDJPGCOM(1)



NAME
       rdjpgcom - display text comments from a JPEG file

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


DESCRIPTION
       rdjpgcom  reads  the  named JPEG/JFIF file, or the standard input if no file is named, and prints any text com-
       ments 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.

OPTIONS
       -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.

HINTS
       rdjpgcom  does not depend on the IJG JPEG library.  Its source code is intended as an illustration of the mini-
       mum 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  digi-
       tal  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.

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

AUTHOR
       Independent JPEG Group



                                 02 April 2009                     RDJPGCOM(1)