WRJPGCOM(1) UNIX System V (15 June 1995) 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
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WRJPGCOM(1) UNIX System V (15 June 1995) WRJPGCOM(1)
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
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