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 com-
       ments 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  some-
       where  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)