rdjpgcom(1) User Commands rdjpgcom(1)NAMErdjpgcom - display text comments from a JPEG file
SYNOPSISrdjpgcom [-verbose] [filename]
DESCRIPTIONrdjpgcom reads the named JPEG or JFIF file, or the standard input if no
file is named, and displays any text comments found in the file on the
standard output.
The JPEG standard allows "comment" (COM) blocks to occur within a JPEG
file. Although the standard does not actually define the intended func‐
tion of COM blocks, they are widely used to hold user-supplied text
strings. This enables you to add annotations, titles, index terms, and
so on to your JPEG files, and later retrieve the COM blocks as text.
COM blocks do not interfere with the image stored in the JPEG file. The
maximum size of a COM block is 64K, but you can have many COM blocks in
one JPEG file.
OPTIONS
The following options are supported:
-verbose Causes rdjpgcom to also display the JPEG image dimen‐
sions.
OPERANDS
The following operands are supported:
filename The name of the JPEG file that contains text comments.
EXTENDED DESCRIPTIONrdjpgcom does not depend on the IJG JPEG library. The rdjpgcom source
code is intended to illustrate the minimum amount of code required to
parse a JPEG file header correctly.
In -verbose mode, rdjpgcom also attempts to display the contents of any
"APP12" markers as text. Some digital cameras produce APP12 markers
that contain useful textual information. You can also modify the source
code to display other APPn marker types.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │image/library/libjpeg │
├─────────────────────────────┼─────────────────────────────┤
│Interface stability │Volatile │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOcjpeg(1), djpeg(1), jpegtran(1), wrjpgcom(1)NOTES
This man page was originally written by the Independent JPEG Group.
Updated by Breda McColgan, Sun Microsystems Inc., 2004.
SunOS 5.11 26 Mar 2004 rdjpgcom(1)
