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1995-01-12
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WRJPGCOM(1) WRJPGCOM(1)
NNAAMMEE
wrjpgcom - insert text comments into a JPEG file
SSYYNNOOPPSSIISS
wwrrjjppggccoomm [ --rreeppllaaccee ] [ --ccoommmmeenntt _t_e_x_t ] [ --ccffiillee _n_a_m_e ] [
_f_i_l_e_n_a_m_e ]
DDEESSCCRRIIPPTTIIOONN
wwrrjjppggccoomm 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.
wwrrjjppggccoomm 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.
OOPPTTIIOONNSS
Switch names may be abbreviated, and are not case sensi
tive.
--rreeppllaaccee
Delete any existing COM blocks from the file.
--ccoommmmeenntt _t_e_x_t
Supply text for new COM block on command line.
--ccffiillee _n_a_m_e
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 --ccoommmmeenntt. 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 --ccoommmmeenntt nor --ccffiillee, then wwrrjjppggccoomm
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
30 August 1994 1
WRJPGCOM(1) WRJPGCOM(1)
comment text entry.
wwrrjjppggccoomm will not add a COM block if the provided comment
string is empty. Therefore --rreeppllaaccee --ccoommmmeenntt """" can be
used to delete all COM blocks from a file.
EEXXAAMMPPLLEESS
Add a short comment to in.jpg, producing out.jpg:
wwrrjjppggccoomm --cc _"_V_i_e_w _o_f _m_y _b_a_c_k _y_a_r_d_" _i_n_._j_p_g >> _o_u_t_._j_p_g
Attach a long comment previously stored in comment.txt:
wwrrjjppggccoomm _i_n_._j_p_g << _c_o_m_m_e_n_t_._t_x_t >> _o_u_t_._j_p_g
or equivalently
wwrrjjppggccoomm --ccffiillee _c_o_m_m_e_n_t_._t_x_t << _i_n_._j_p_g >> _o_u_t_._j_p_g
SSEEEE AALLSSOO
ccjjppeegg(1), ddjjppeegg(1), rrddjjppggccoomm(1)
AAUUTTHHOORR
Independent JPEG Group
30 August 1994 2