WRJPGCOM(1) User Commands 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)