RDJPGCOM(1)                                         RDJPGCOM(1)





NAME
       rdjpgcom - display text comments from a JPEG file

SYNOPSIS
       rdjpgcom [ -verbose ] [ filename ]


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

       Switch names may be abbreviated, and are not case sensi-
       tive.

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 tex-
       tual  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



                        11 October 1997             RDJPGCOM(1)
