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Merge from eCos master repository on 2002-05-20-20:11:54-BST
author jlarmour
date Mon, 20 May 2002 22:19:26 +0000
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1 .TH RDJPGCOM 1 "11 October 1997"
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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 \-verbose
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8 ]
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9 [
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10 .I filename
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11 ]
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12 .LP
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13 .SH DESCRIPTION
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14 .LP
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15 .B rdjpgcom
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16 reads the named JPEG/JFIF file, or the standard input if no file is named,
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17 and prints any text comments found in the file on the standard output.
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18 .PP
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19 The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.
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20 Although the standard doesn't actually define what COM blocks are for, they
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21 are widely used to hold user-supplied text strings. This lets you add
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22 annotations, titles, index terms, etc to your JPEG files, and later retrieve
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23 them as text. COM blocks do not interfere with the image stored in the JPEG
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24 file. The maximum size of a COM block is 64K, but you can have as many of
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25 them as you like in one JPEG file.
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26 .SH OPTIONS
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27 .TP
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28 .B \-verbose
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29 Causes
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30 .B rdjpgcom
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31 to also display the JPEG image dimensions.
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32 .PP
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33 Switch names may be abbreviated, and are not case sensitive.
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34 .SH HINTS
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35 .B rdjpgcom
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36 does not depend on the IJG JPEG library. Its source code is intended as an
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37 illustration of the minimum amount of code required to parse a JPEG file
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38 header correctly.
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39 .PP
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40 In
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41 .B \-verbose
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42 mode,
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43 .B rdjpgcom
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44 will also attempt to print the contents of any "APP12" markers as text.
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45 Some digital cameras produce APP12 markers containing useful textual
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46 information. If you like, you can modify the source code to print
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47 other APPn marker types as well.
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48 .SH SEE ALSO
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49 .BR cjpeg (1),
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50 .BR djpeg (1),
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51 .BR jpegtran (1),
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52 .BR wrjpgcom (1)
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53 .SH AUTHOR
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54 Independent JPEG Group