1 | .TH RDJPGCOM 1 "02 April 2009"
|
---|
2 | .SH NAME
|
---|
3 | rdjpgcom \- display text comments from a JPEG file
|
---|
4 | .SH SYNOPSIS
|
---|
5 | .B rdjpgcom
|
---|
6 | [
|
---|
7 | .B \-raw
|
---|
8 | ]
|
---|
9 | [
|
---|
10 | .B \-verbose
|
---|
11 | ]
|
---|
12 | [
|
---|
13 | .I filename
|
---|
14 | ]
|
---|
15 | .LP
|
---|
16 | .SH DESCRIPTION
|
---|
17 | .LP
|
---|
18 | .B rdjpgcom
|
---|
19 | reads the named JPEG/JFIF file, or the standard input if no file is named,
|
---|
20 | and prints any text comments found in the file on the standard output.
|
---|
21 | .PP
|
---|
22 | The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.
|
---|
23 | Although the standard doesn't actually define what COM blocks are for, they
|
---|
24 | are widely used to hold user-supplied text strings. This lets you add
|
---|
25 | annotations, titles, index terms, etc to your JPEG files, and later retrieve
|
---|
26 | them as text. COM blocks do not interfere with the image stored in the JPEG
|
---|
27 | file. The maximum size of a COM block is 64K, but you can have as many of
|
---|
28 | them as you like in one JPEG file.
|
---|
29 | .SH OPTIONS
|
---|
30 | .TP
|
---|
31 | .B \-raw
|
---|
32 | Normally
|
---|
33 | .B rdjpgcom
|
---|
34 | escapes non-printable characters in comments, for security reasons.
|
---|
35 | This option avoids that.
|
---|
36 | .PP
|
---|
37 | .B \-verbose
|
---|
38 | Causes
|
---|
39 | .B rdjpgcom
|
---|
40 | to also display the JPEG image dimensions.
|
---|
41 | .PP
|
---|
42 | Switch names may be abbreviated, and are not case sensitive.
|
---|
43 | .SH HINTS
|
---|
44 | .B rdjpgcom
|
---|
45 | does not depend on the IJG JPEG library. Its source code is intended as an
|
---|
46 | illustration of the minimum amount of code required to parse a JPEG file
|
---|
47 | header correctly.
|
---|
48 | .PP
|
---|
49 | In
|
---|
50 | .B \-verbose
|
---|
51 | mode,
|
---|
52 | .B rdjpgcom
|
---|
53 | will also attempt to print the contents of any "APP12" markers as text.
|
---|
54 | Some digital cameras produce APP12 markers containing useful textual
|
---|
55 | information. If you like, you can modify the source code to print
|
---|
56 | other APPn marker types as well.
|
---|
57 | .SH SEE ALSO
|
---|
58 | .BR cjpeg (1),
|
---|
59 | .BR djpeg (1),
|
---|
60 | .BR jpegtran (1),
|
---|
61 | .BR wrjpgcom (1)
|
---|
62 | .SH AUTHOR
|
---|
63 | Independent JPEG Group
|
---|