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| Rev | Author | Line No. | Line |
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| 244 | chris | 1 | .TH RDJPGCOM 1 "11 October 1997" |
| 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 |