RDJPGCOM(1)						      General Commands Manual						       RDJPGCOM(1)

NAME

       rdjpgcom - display text comments from a JPEG file

SYNOPSIS

       rdjpgcom [ -raw ] [ -verbose ] [ filename ]

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(1), djpeg(1), jpegtran(1), wrjpgcom(1)

AUTHOR

       Independent JPEG Group

								   02 April 2009						       RDJPGCOM(1)