103 lines
2.5 KiB
Groff
103 lines
2.5 KiB
Groff
.TH WRJPGCOM 1 "30 August 1994"
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.SH NAME
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wrjpgcom \- insert text comments into a JPEG file
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.SH SYNOPSIS
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.B wrjpgcom
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[
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.B \-replace
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]
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[
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.BI \-comment " text"
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]
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[
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.BI \-cfile " name"
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]
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[
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.I filename
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]
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.LP
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.SH DESCRIPTION
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.LP
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.B wrjpgcom
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reads the named JPEG/JFIF file, or the standard input if no file is named,
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and generates a new JPEG/JFIF file on standard output. A comment block is
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added to the file.
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.PP
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The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.
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Although the standard doesn't actually define what COM blocks are for, they
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are widely used to hold user-supplied text strings. This lets you add
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annotations, titles, index terms, etc to your JPEG files, and later retrieve
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them as text. COM blocks do not interfere with the image stored in the JPEG
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file. The maximum size of a COM block is 64K, but you can have as many of
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them as you like in one JPEG file.
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.PP
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.B wrjpgcom
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adds a COM block, containing text you provide, to a JPEG file.
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Ordinarily, the COM block is added after any existing COM blocks; but you
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can delete the old COM blocks if you wish.
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.SH OPTIONS
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Switch names may be abbreviated, and are not case sensitive.
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.TP
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.B \-replace
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Delete any existing COM blocks from the file.
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.TP
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.BI \-comment " text"
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Supply text for new COM block on command line.
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.TP
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.BI \-cfile " name"
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Read text for new COM block from named file.
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.PP
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If you have only one line of comment text to add, you can provide it on the
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command line with
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.BR \-comment .
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The comment text must be surrounded with quotes so that it is treated as a
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single argument. Longer comments can be read from a text file.
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.PP
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If you give neither
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.B \-comment
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nor
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.BR \-cfile ,
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then
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.B wrjpgcom
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will read the comment text from standard input. (In this case an input image
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file name MUST be supplied, so that the source JPEG file comes from somewhere
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else.) You can enter multiple lines, up to 64KB worth. Type an end-of-file
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indicator (usually control-D) to terminate the comment text entry.
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.PP
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.B wrjpgcom
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will not add a COM block if the provided comment string is empty. Therefore
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\fB\-replace \-comment ""\fR can be used to delete all COM blocks from a file.
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.SH EXAMPLES
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.LP
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Add a short comment to in.jpg, producing out.jpg:
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.IP
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.B wrjpgcom \-c
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\fI"View of my back yard" in.jpg
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.B >
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.I out.jpg
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.PP
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Attach a long comment previously stored in comment.txt:
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.IP
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.B wrjpgcom
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.I in.jpg
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.B <
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.I comment.txt
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.B >
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.I out.jpg
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.PP
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or equivalently
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.IP
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.B wrjpgcom
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.B -cfile
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.I comment.txt
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.B <
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.I in.jpg
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.B >
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.I out.jpg
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.SH SEE ALSO
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.BR cjpeg (1),
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.BR djpeg (1),
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.BR rdjpgcom (1)
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.SH AUTHOR
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Independent JPEG Group
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