WRJPGCOM(1)                                           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  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 inter-
       fere  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  sensi-
       tive.

       -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  com-
       ment 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                         1