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wrjpgcom(1)


NAME

   wrjpgcom - insert text comments into a JPEG file

SYNOPSIS

   wrjpgcom [ -replace ] [ -comment text ] [ -cfile name ] [ filename ]

DESCRIPTION

   wrjpgcom  reads  the  named JPEG/JFIF file, or the standard input if no
   file is named, and generates a new JPEG/JFIF file on  standard  output.
   A comment block is added to the file.

   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.

   wrjpgcom adds a COM block, containing text you provide, to a JPEG file.
   Ordinarily, the COM block is added after any existing COM  blocks;  but
   you can delete the old COM blocks if you wish.

OPTIONS

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

   -replace
          Delete any existing COM blocks from the file.

   -comment text
          Supply text for new COM block on command line.

   -cfile name
          Read text for new COM block from named file.

   If you have only one line of comment text to add, you can provide it on
   the command line with -comment.  The comment text  must  be  surrounded
   with  quotes  so  that  it  is  treated  as  a single argument.  Longer
   comments can be read from a text file.

   If you give neither -comment nor -cfile, then wrjpgcom  will  read  the
   comment  text  from  standard input.  (In this case an input image file
   name MUST be  supplied,  so  that  the  source  JPEG  file  comes  from
   somewhere else.)  You can enter multiple lines, up to 64KB worth.  Type
   an end-of-file indicator (usually control-D) to terminate  the  comment
   text entry.

   wrjpgcom  will  not  add  a COM block if the provided comment string is
   empty.  Therefore -replace -comment "" can be used to  delete  all  COM
   blocks from a file.

EXAMPLES

   Add a short comment to in.jpg, producing out.jpg:

          wrjpgcom -c "View of my back yard" in.jpg > out.jpg

   Attach a long comment previously stored in comment.txt:

          wrjpgcom in.jpg < comment.txt > out.jpg

   or equivalently

          wrjpgcom -cfile comment.txt < in.jpg > out.jpg

SEE ALSO

   cjpeg(1), djpeg(1), jpegtran(1), rdjpgcom(1)

AUTHOR

   Independent JPEG Group

                             15 June 1995                      WRJPGCOM(1)



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