1 .TH WRJPGCOM 1 "15 June 1995"

     2 .SH NAME

     3 wrjpgcom \- insert text comments into a JPEG file

     4 .SH SYNOPSIS

     5 .B wrjpgcom

     6 [

     7 .B \-replace

     8 ]

     9 [

    10 .BI \-comment " text"

    11 ]

    12 [

    13 .BI \-cfile " name"

    14 ]

    15 [

    16 .I filename

    17 ]

    18 .LP

    19 .SH DESCRIPTION

    20 .LP

    21 .B wrjpgcom

    22 reads the named JPEG/JFIF file, or the standard input if no file is named,

    23 and generates a new JPEG/JFIF file on standard output.  A comment block is

    24 added to the file.

    25 .PP

    26 The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.

    27 Although the standard doesn't actually define what COM blocks are for, they

    28 are widely used to hold user-supplied text strings.  This lets you add

    29 annotations, titles, index terms, etc to your JPEG files, and later retrieve

    30 them as text.  COM blocks do not interfere with the image stored in the JPEG

    31 file.  The maximum size of a COM block is 64K, but you can have as many of

    32 them as you like in one JPEG file.

    33 .PP

    34 .B wrjpgcom

    35 adds a COM block, containing text you provide, to a JPEG file.

    36 Ordinarily, the COM block is added after any existing COM blocks; but you

    37 can delete the old COM blocks if you wish.

    38 .SH OPTIONS

    39 Switch names may be abbreviated, and are not case sensitive.

    40 .TP

    41 .B \-replace

    42 Delete any existing COM blocks from the file.

    43 .TP

    44 .BI \-comment " text"

    45 Supply text for new COM block on command line.

    46 .TP

    47 .BI \-cfile " name"

    48 Read text for new COM block from named file.

    49 .PP

    50 If you have only one line of comment text to add, you can provide it on the

    51 command line with

    52 .BR \-comment .

    53 The comment text must be surrounded with quotes so that it is treated as a

    54 single argument.  Longer comments can be read from a text file.

    55 .PP

    56 If you give neither

    57 .B \-comment

    58 nor

    59 .BR \-cfile ,

    60 then

    61 .B wrjpgcom

    62 will read the comment text from standard input.  (In this case an input image

    63 file name MUST be supplied, so that the source JPEG file comes from somewhere

    64 else.)  You can enter multiple lines, up to 64KB worth.  Type an end-of-file

    65 indicator (usually control-D) to terminate the comment text entry.

    66 .PP

    67 .B wrjpgcom

    68 will not add a COM block if the provided comment string is empty.  Therefore

    69 \fB\-replace \-comment ""\fR can be used to delete all COM blocks from a file.

    70 .SH EXAMPLES

    71 .LP

    72 Add a short comment to in.jpg, producing out.jpg:

    73 .IP

    74 .B wrjpgcom \-c

    75 \fI"View of my back yard" in.jpg

    76 .B >

    77 .I out.jpg

    78 .PP

    79 Attach a long comment previously stored in comment.txt:

    80 .IP

    81 .B wrjpgcom

    82 .I in.jpg

    83 .B <

    84 .I comment.txt

    85 .B >

    86 .I out.jpg

    87 .PP

    88 or equivalently

    89 .IP

    90 .B wrjpgcom

    91 .B -cfile

    92 .I comment.txt

    93 .B <

    94 .I in.jpg

    95 .B >

    96 .I out.jpg

    97 .SH SEE ALSO

    98 .BR cjpeg (1),

    99 .BR djpeg (1),

   100 .BR jpegtran (1),

   101 .BR rdjpgcom (1)

   102 .SH AUTHOR

   103 Independent JPEG Group