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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