| 1 | .TH RDJPGCOM 1 "02 April 2009"
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| 2 | .SH NAME
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| 3 | rdjpgcom \- display text comments from a JPEG file
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| 4 | .SH SYNOPSIS
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| 5 | .B rdjpgcom
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| 6 | [
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| 7 | .B \-raw
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| 8 | ]
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| 9 | [
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| 10 | .B \-verbose
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| 11 | ]
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| 12 | [
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| 13 | .I filename
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| 14 | ]
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| 15 | .LP
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| 16 | .SH DESCRIPTION
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| 17 | .LP
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| 18 | .B rdjpgcom
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| 19 | reads the named JPEG/JFIF file, or the standard input if no file is named,
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| 20 | and prints any text comments found in the file on the standard output.
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| 21 | .PP
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| 22 | The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.
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| 23 | Although the standard doesn't actually define what COM blocks are for, they
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| 24 | are widely used to hold user-supplied text strings. This lets you add
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| 25 | annotations, titles, index terms, etc to your JPEG files, and later retrieve
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| 26 | them as text. COM blocks do not interfere with the image stored in the JPEG
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| 27 | file. The maximum size of a COM block is 64K, but you can have as many of
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| 28 | them as you like in one JPEG file.
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| 29 | .SH OPTIONS
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| 30 | .TP
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| 31 | .B \-raw
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| 32 | Normally
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| 33 | .B rdjpgcom
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| 34 | escapes non-printable characters in comments, for security reasons.
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| 35 | This option avoids that.
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| 36 | .PP
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| 37 | .B \-verbose
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| 38 | Causes
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| 39 | .B rdjpgcom
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| 40 | to also display the JPEG image dimensions.
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| 41 | .PP
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| 42 | Switch names may be abbreviated, and are not case sensitive.
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| 43 | .SH HINTS
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| 44 | .B rdjpgcom
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| 45 | does not depend on the IJG JPEG library. Its source code is intended as an
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| 46 | illustration of the minimum amount of code required to parse a JPEG file
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| 47 | header correctly.
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| 48 | .PP
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| 49 | In
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| 50 | .B \-verbose
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| 51 | mode,
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| 52 | .B rdjpgcom
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| 53 | will also attempt to print the contents of any "APP12" markers as text.
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| 54 | Some digital cameras produce APP12 markers containing useful textual
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| 55 | information. If you like, you can modify the source code to print
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| 56 | other APPn marker types as well.
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| 57 | .SH SEE ALSO
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| 58 | .BR cjpeg (1),
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| 59 | .BR djpeg (1),
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| 60 | .BR jpegtran (1),
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| 61 | .BR wrjpgcom (1)
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| 62 | .SH AUTHOR
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| 63 | Independent JPEG Group
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