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| author | jpayne |
|---|---|
| date | Tue, 18 Mar 2025 16:23:26 -0400 |
| parents | |
| children |
| rev | line source |
|---|---|
| jpayne@68 | 1 .TH RDJPGCOM 1 "13 September 2013" |
| jpayne@68 | 2 .SH NAME |
| jpayne@68 | 3 rdjpgcom \- display text comments from a JPEG file |
| jpayne@68 | 4 .SH SYNOPSIS |
| jpayne@68 | 5 .B rdjpgcom |
| jpayne@68 | 6 [ |
| jpayne@68 | 7 .B \-raw |
| jpayne@68 | 8 ] |
| jpayne@68 | 9 [ |
| jpayne@68 | 10 .B \-verbose |
| jpayne@68 | 11 ] |
| jpayne@68 | 12 [ |
| jpayne@68 | 13 .I filename |
| jpayne@68 | 14 ] |
| jpayne@68 | 15 .LP |
| jpayne@68 | 16 .SH DESCRIPTION |
| jpayne@68 | 17 .LP |
| jpayne@68 | 18 .B rdjpgcom |
| jpayne@68 | 19 reads the named JPEG/JFIF file, or the standard input if no file is named, |
| jpayne@68 | 20 and prints any text comments found in the file on the standard output. |
| jpayne@68 | 21 .PP |
| jpayne@68 | 22 The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file. |
| jpayne@68 | 23 Although the standard doesn't actually define what COM blocks are for, they |
| jpayne@68 | 24 are widely used to hold user-supplied text strings. This lets you add |
| jpayne@68 | 25 annotations, titles, index terms, etc to your JPEG files, and later retrieve |
| jpayne@68 | 26 them as text. COM blocks do not interfere with the image stored in the JPEG |
| jpayne@68 | 27 file. The maximum size of a COM block is 64K, but you can have as many of |
| jpayne@68 | 28 them as you like in one JPEG file. |
| jpayne@68 | 29 .SH OPTIONS |
| jpayne@68 | 30 .TP |
| jpayne@68 | 31 .B \-raw |
| jpayne@68 | 32 Normally |
| jpayne@68 | 33 .B rdjpgcom |
| jpayne@68 | 34 escapes non-printable characters in comments, for security reasons. |
| jpayne@68 | 35 This option avoids that. |
| jpayne@68 | 36 .PP |
| jpayne@68 | 37 .B \-verbose |
| jpayne@68 | 38 Causes |
| jpayne@68 | 39 .B rdjpgcom |
| jpayne@68 | 40 to also display the JPEG image dimensions. |
| jpayne@68 | 41 .PP |
| jpayne@68 | 42 Switch names may be abbreviated, and are not case sensitive. |
| jpayne@68 | 43 .SH HINTS |
| jpayne@68 | 44 .B rdjpgcom |
| jpayne@68 | 45 does not depend on the IJG JPEG library. Its source code is intended as an |
| jpayne@68 | 46 illustration of the minimum amount of code required to parse a JPEG file |
| jpayne@68 | 47 header correctly. |
| jpayne@68 | 48 .PP |
| jpayne@68 | 49 In |
| jpayne@68 | 50 .B \-verbose |
| jpayne@68 | 51 mode, |
| jpayne@68 | 52 .B rdjpgcom |
| jpayne@68 | 53 will also attempt to print the contents of any "APP12" markers as text. |
| jpayne@68 | 54 Some digital cameras produce APP12 markers containing useful textual |
| jpayne@68 | 55 information. If you like, you can modify the source code to print |
| jpayne@68 | 56 other APPn marker types as well. |
| jpayne@68 | 57 .SH SEE ALSO |
| jpayne@68 | 58 .BR cjpeg (1), |
| jpayne@68 | 59 .BR djpeg (1), |
| jpayne@68 | 60 .BR jpegtran (1), |
| jpayne@68 | 61 .BR wrjpgcom (1) |
| jpayne@68 | 62 .SH AUTHOR |
| jpayne@68 | 63 Independent JPEG Group |