RDJPGCOM(1) - man - phpman

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  illus‐
       tration 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)