| Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 1 | .TH RDJPGCOM 1 "11 October 1997" |
| Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 2 | .SH NAME |
| 3 | rdjpgcom \- display text comments from a JPEG file |
| 4 | .SH SYNOPSIS |
| 5 | .B rdjpgcom |
| 6 | [ |
| 7 | .B \-verbose |
| 8 | ] |
| 9 | [ |
| 10 | .I filename |
| 11 | ] |
| 12 | .LP |
| 13 | .SH DESCRIPTION |
| 14 | .LP |
| 15 | .B rdjpgcom |
| 16 | reads the named JPEG/JFIF file, or the standard input if no file is named, |
| 17 | and prints any text comments found in the file on the standard output. |
| 18 | .PP |
| 19 | The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file. |
| 20 | Although the standard doesn't actually define what COM blocks are for, they |
| 21 | are widely used to hold user-supplied text strings. This lets you add |
| 22 | annotations, titles, index terms, etc to your JPEG files, and later retrieve |
| 23 | them as text. COM blocks do not interfere with the image stored in the JPEG |
| 24 | file. The maximum size of a COM block is 64K, but you can have as many of |
| 25 | them as you like in one JPEG file. |
| 26 | .SH OPTIONS |
| 27 | .TP |
| 28 | .B \-verbose |
| 29 | Causes |
| 30 | .B rdjpgcom |
| 31 | to also display the JPEG image dimensions. |
| 32 | .PP |
| 33 | Switch names may be abbreviated, and are not case sensitive. |
| 34 | .SH HINTS |
| 35 | .B rdjpgcom |
| 36 | does not depend on the IJG JPEG library. Its source code is intended as an |
| 37 | illustration of the minimum amount of code required to parse a JPEG file |
| 38 | header correctly. |
| Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 39 | .PP |
| 40 | In |
| 41 | .B \-verbose |
| 42 | mode, |
| 43 | .B rdjpgcom |
| 44 | will also attempt to print the contents of any "APP12" markers as text. |
| 45 | Some digital cameras produce APP12 markers containing useful textual |
| 46 | information. If you like, you can modify the source code to print |
| 47 | other APPn marker types as well. |
| Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 48 | .SH SEE ALSO |
| 49 | .BR cjpeg (1), |
| 50 | .BR djpeg (1), |
| Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 51 | .BR jpegtran (1), |
| Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 52 | .BR wrjpgcom (1) |
| 53 | .SH AUTHOR |
| 54 | Independent JPEG Group |