wrjpgcom
insert text comments into a JPEG file
see also :
cjpeg - djpeg - jpegtran - rdjpgcom
Synopsis
wrjpgcom
[ -replace ] [ -comment
text ] [ -cfile name ] [
filename ]
add an example, a script, a trick and tips
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
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.
see also
cjpeg ,
djpeg , jpegtran , rdjpgcom
author
Independent
JPEG Group