source: trunk/libjpeg/rdjpgcom.1 @ 136

Last change on this file since 136 was 15, checked in by Eugene Romanenko, 16 years ago

needed libs update

File size: 1.6 KB
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1.TH RDJPGCOM 1 "11 October 1997"
2.SH NAME
3rdjpgcom \- 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
16reads the named JPEG/JFIF file, or the standard input if no file is named,
17and prints any text comments found in the file on the standard output.
18.PP
19The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.
20Although the standard doesn't actually define what COM blocks are for, they
21are widely used to hold user-supplied text strings.  This lets you add
22annotations, titles, index terms, etc to your JPEG files, and later retrieve
23them as text.  COM blocks do not interfere with the image stored in the JPEG
24file.  The maximum size of a COM block is 64K, but you can have as many of
25them as you like in one JPEG file.
26.SH OPTIONS
27.TP
28.B \-verbose
29Causes
30.B rdjpgcom
31to also display the JPEG image dimensions.
32.PP
33Switch names may be abbreviated, and are not case sensitive.
34.SH HINTS
35.B rdjpgcom
36does not depend on the IJG JPEG library.  Its source code is intended as an
37illustration of the minimum amount of code required to parse a JPEG file
38header correctly.
39.PP
40In
41.B \-verbose
42mode,
43.B rdjpgcom
44will also attempt to print the contents of any "APP12" markers as text.
45Some digital cameras produce APP12 markers containing useful textual
46information.  If you like, you can modify the source code to print
47other APPn marker types as well.
48.SH SEE ALSO
49.BR cjpeg (1),
50.BR djpeg (1),
51.BR jpegtran (1),
52.BR wrjpgcom (1)
53.SH AUTHOR
54Independent JPEG Group
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