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  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 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 comment text entry.

       wrjpgcom  will  not add a COM block if the provided com-
       ment 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)
