rdjpgcom
display text comments from a JPEG file
see also :
cjpeg - djpeg - jpegtran - wrjpgcom
Synopsis
rdjpgcom
[ -raw ] [ -verbose ] [
filename ]
add an example, a script, a trick and tips
examples
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description
rdjpgcom
reads the named JPEG/JFIF file, or the standard input if no
file is named, and prints 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 doesn’t
actually define what COM blocks are for, they are widely
used to hold user-supplied text strings. This lets you add
annotations, titles, index terms, etc to your JPEG files,
and later retrieve them 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 as many of them as you
like in one JPEG file.
options
-raw
Normally rdjpgcom escapes
non-printable characters in comments, for security reasons.
This option avoids that.
-verbose
Causes rdjpgcom to also display the JPEG image
dimensions.
Switch names
may be abbreviated, and are not case sensitive.
hints
rdjpgcom does not depend on the IJG JPEG library. Its
source code is intended as an illustration of the minimum amount
of code required to parse a JPEG file header correctly.
In -verbose mode, rdjpgcom will also attempt to
print the contents of any "APP12" markers as text. Some digital
cameras produce APP12 markers containing useful textual
information. If you like, you can modify the source code to print
other APPn marker types as well.
see also
cjpeg ,
djpeg , jpegtran , wrjpgcom
author
Independent
JPEG Group